This work examines China's mainstream journal ranking system from the Chinese Academy of Science (CAS), including its history, recent reforms, and current operation, with a particular focus on Physics of Fluids. Using official statistics, this paper analyzes the Physics of Fluids standings in the CAS system from 2015 to 2023. During these years, Physics of Fluids experienced a significant increase in both popularity and impact. Meanwhile, the CAS system underwent substantial reforms, including the newly proposed Advanced edition, which universally boosted fluids journal academic weights in China. Most notably, the brand-new Field Normalized Citation Success Index (期刊超越指数 or FNCSI) offered a new lens through which to assess academic journal impact. Statistics reveal that Physics of Fluids is in a promising position to become the fourth Tier 1 fluids journal to enter any of CAS's Major Categories (after the Annual Review of Fluid Mechanics, Nuclear Fusion, and Plasma Sources Sciences and Technology) and the first-ever non-review-only Tier 1 fluids journal to enter the Engineering and Technology (工程技术 E&T) Major Category. Finally, this paper suggests several directions for Physics of Fluids to direct future endeavors as it enjoys heightening popularity in China.

China's determined rise in academics and research makes its perspective on journal significance a matter of global interest. There are two widely accepted journal ranking systems in China: The Journal Citation Reports system (JCR) of Clarivate Analytics, which is the mainstream system worldwide,1 and the Chinese Academy of Science system (CAS), tailored for China's academia.2 Both systems are closely related to the Science Citation Index Extend (SCIE) and Social Science Citation Index (SSCI) indices. Whereas, CAS includes Chinese journals from the Emerging Sources Citation Index (ESCI), the JCR does not.

Given the significant differences between Chinese and Western academia, there may be confusion regarding how the two systems operate, co-exist, and complement each other in China. As more international journals aim to bridge the gap and reach out to more Chinese authors and readers, there is an urgent need to explain the CAS system. This article first provides a brief history of the CAS system, its reformation, and its operational model. It will then offer official statistics and analytical insights into where Physics of Fluids stands in the CAS system and recommendations for future endeavours in China.

The content and data used in this work have all been obtained directly from the CAS and Clarivate websites through the library subscriptions of Chongqing University and Liaoning Technical University.1,2 The important work of Tong et al.3 from the National Science Library of the Chinese Academy of Sciences and the University of the Chinese Academy of Sciences is also a central reference.

The CAS Journal Ranking System began its development in 2000 and saw its first edition published in 2004 to counteract the misuse of the journal Impact Factor (IF) in China. Its primary motivation was to provide a universally understood, cross-discipline index that quantifies a journal's significance with consideration of academic disciplinary heterogeneity and uneven levels of impact. As of 2004, the JCR system comprised 176 disciplines, which the CAS then deemed divided too finely. Thus, while adopting the 176 JCR disciplines as Minor Categories (小类), the CAS crafted the 13 overarching Major Categories (大类) of Table I.

TABLE I.

The 13 Major Categories of the CAS Basic edition.

Major Category (Mandarin) Major Category (Translated)
数学  Mathematics 
物理  Physics 
化学  Chemistry 
生物  Biology 
地学  Earth Science 
天文  Astronomy 
工程技术  Engineering and Technology 
医学  Medicine 
环境科学  Environmental Science 
10  农林科学  Agricultural and Forestry Science 
11  社会科学  Social Science 
12  管理科学  Management Science 
13  综合性期刊  Multidisciplinary Science 
Major Category (Mandarin) Major Category (Translated)
数学  Mathematics 
物理  Physics 
化学  Chemistry 
生物  Biology 
地学  Earth Science 
天文  Astronomy 
工程技术  Engineering and Technology 
医学  Medicine 
环境科学  Environmental Science 
10  农林科学  Agricultural and Forestry Science 
11  社会科学  Social Science 
12  管理科学  Management Science 
13  综合性期刊  Multidisciplinary Science 

The distribution systems employed by the JCR and CAS differ significantly. The JCR uses a quartile distribution, where Q1 corresponds to the top 25%, Q2 to 26%–50%, Q3 to 51%–75%, and Q4 to 76%–100%. Conversely, the CAS adopts arbitrarily the roughly pyramidal distribution, suggested by Jin and Wang,4 where Tier 1 corresponds to the top 5%, Tier 2 to 6%–20%, Tier 3 to 21%–50%, and Tier 4 to 51%–100% (see arbitrarily chosen cut-offs of pyramid of Table III). Consequently, it is considerably more challenging for a journal to attain Tier 1 status in the CAS system than Q1 status in JCR. A journal ranks Q1 in JCR may fall into Tier 1, 2, or 3 in the CAS system. Whereas JCR rankings revolve around the quartile system, the CAS ranking systems (both Basic and Advanced), rely on pyramidal distributions.

The original CAS system utilized the three-year IF as the ranking index, in contrast to the JCR one-year IF. The intention was to minimize manipulation or short-term fluctuation. Before 2019, the Basic edition was the sole version of the CAS system. However, in 2019, the CAS released an Advanced edition (升级版) that, though not immediately, eventually superseded the Basic edition that stopped permanently in 2022.

The primary motivation for the Advanced edition is to overcome the apparent limitations of the Basic edition as observed in practice after years in force.3 The first of these apparent limitations was that, even though the three-year IF intended to minimize the impact of skewed citation distributions, the Basic edition was far from ideal, as occasionally, highly cited entries still led to marked reflections on a journal's IF, leaving room for manipulation. The second limitation was that the base IF and citation potential varied significantly across document types, so the tendency to publish review papers was alarmingly high. The third limitation was the suboptimal category division, which demanded a finer classification.

From 2019 to 2021, both the Basic and Advanced editions were in use as part of a transitional phase. The Advanced edition differs from its predecessor in several ways. First, the original 13 Major Categories have been reorganized, renamed, and expanded to include the 18 new entries of Table II. Second, the Minor Categories have also been expanded to encompass 254 disciplines, aligning with the newest expansions of the JCR system. Last, with the intention to part ways with IF-inherent limitations, the ranking index has been revised from the three-year IF to the newly proposed Field Normalized Citation Success Index (期刊超越指数 or FNCSI). Table III compares the modus operandi of the JCR and CAS Advanced edition.

TABLE II.

The 18 Major Categories of the CAS Advanced edition.

Legend: Newly added Regrouped & renamed
Major Category (Mandarin) Major Category (Translated)
数学  Mathematics 
物理和天体物理  Physics and Astrophysics 
化学  Chemistry 
生物  Biology 
地学  Earth Science 
教育学  Education 
工程技术  Engineering and Technology 
医学  Medicine 
环境科学和生态学  Environmental Science and Ecology 
10  农林科学  Agricultural and Forestry Science 
11  社会科学  Social Science 
12  管理科学  Management Science 
13  综合性期刊  Multidisciplinary Science 
14  材料科学  Material Science 
15  计算机科学  Computer Science 
16  法学  Law 
17  心理学  Psychology 
18  人文科学  Human Science 
Legend: Newly added Regrouped & renamed
Major Category (Mandarin) Major Category (Translated)
数学  Mathematics 
物理和天体物理  Physics and Astrophysics 
化学  Chemistry 
生物  Biology 
地学  Earth Science 
教育学  Education 
工程技术  Engineering and Technology 
医学  Medicine 
环境科学和生态学  Environmental Science and Ecology 
10  农林科学  Agricultural and Forestry Science 
11  社会科学  Social Science 
12  管理科学  Management Science 
13  综合性期刊  Multidisciplinary Science 
14  材料科学  Material Science 
15  计算机科学  Computer Science 
16  法学  Law 
17  心理学  Psychology 
18  人文科学  Human Science 
TABLE III.

Comparison between the JCR and CAS Advanced Edition.

JCRCAS Advanced Edition
Inclusion SCI + SSCI SCI + SSCI + Selected ESCI 
Discipline 254 disciplines 18 Major Categories 254 Minor Categories 
Ranking Index Impact Factor (IF) Field Normalized Citation Success Index (FNCSI) 
Division Q1 to Q4 according to IF Tier 1 to Tier 4 according to FNCSI 
Distribution   
JCRCAS Advanced Edition
Inclusion SCI + SSCI SCI + SSCI + Selected ESCI 
Discipline 254 disciplines 18 Major Categories 254 Minor Categories 
Ranking Index Impact Factor (IF) Field Normalized Citation Success Index (FNCSI) 
Division Q1 to Q4 according to IF Tier 1 to Tier 4 according to FNCSI 
Distribution   
To understand the FNCSI, one should first understand how the IF is defined.2 For instance, the IF in 2022 is
IF 2022  ≡  c 2023 , 2021 2022 p 2021 + p 2022 ,
(1)
where c 2023 , 2021 2022 is citations in 2023 from all publications in 2021–2022 and p 2021 and p 2022 are publications in years 2021 and 2022, respectively. While the IF is a simple and transparent method for assessing a journal's importance, it ignores (i) citations in the calendar year of publication, which in turn punishes immediacy, efficiency in peer review, and publishing speed, and (ii) the punishing effect of journal growth on this bibliographic metric.5 Consequently, there has been ongoing debate within China's academic community regarding the reliability of IF as a ranking metric. Years of operation with the three-year IF also deemed it unsatisfactory, particularly given the significant differences in popularity across research disciplines—a second-tier journal from a popular field may have an IF many times higher than that of a top-tier journal in an underrepresented subfield.
The CAS thus proposed the FNCSI in 2019.3 The probability that the citation of a paper from journal A is larger than a random paper on the same topic and with the same document type from other journals is given by
S A = P c a > c o | a A , o O = t , d P A t , d P c a > c o | a A t , d , o O t , d ,
(2)
where ca is the citation count of one paper from Journal A, t  ∈  { topic 1 , topic 2 , topic 3 , }, d  ∈  { article, review }, A t , d is the collection of publications of type d on topic t in journal A, and O is the collection of publications from the other journal, and where SA is the FNCSI. Thus, FNCSI is the probability of a publication in journal A receiving a higher citation count than another random publication of the same topic and publication type from another journal. Of course, on first reading, even one well-versed in statistical mechanics will find Eq. (2) difficult to comprehend. Whereas IF of Eq. (1) excludes same calendar year cites and punishes journal growth,5 FNSCI of Eq. (2) does count same calendar year cites, and needs no growth-adjustment. There is no impact factor associated with CAS rankings in the latest Advanced version (see Subsection II A). There is no FNSCI associated with CAS rankings in the Basic version (see Subsection II A).
For a specific topic t, its FNCSI S A t is calculated by
S A t = 1 N A t d N A t A t , d , o O t , d 1 c a > c o + A t , d , o O t , d 0.5 c a = c o N A t , d N O t , d ,
(3)
where weight 1 is for ca > co and 0.5 for ca = co. Journal A usually involves several research topics; then the total FNCSI SA can be summed as below:
S A 1 N A t N A t S A t ,
(4)
where N A t is the number of publications of journal A on topic t based on a two-year citation window. Equations (3) and (4) deepen our understanding of Eq. (2).

So, field normalizing actually means normalizing by topic. For instance, a journal publishing papers on turbulence improves its ranking when normalized by all other papers on turbulence (be they published in fluids journals or turbulence journals or general science journals)

FNCSI is the probability of a publication in journal A receiving a higher citation count than another random publication of the same topic and publication type from another journal. One trend Tong et al.3 have observed by comparing the FNCSI and their Field-Normalized Impact Factor (FNIF), defined in the fourth equation of Subsection 3.3 of Ref. 3, is that the former significantly downplays the influence of individual highly cited papers. They used the telling example of Chinese Physics: C—70% of its papers have no citations, and one paper has more than 2000. Journals of this characteristic generally suffered in the FNCSI ranking system. The new index penalizes the IF stat players, and the random paper selection process also asks journals to aim for collective improvement instead of individual success. In other words, papers with few or no citations will now hurt a journal much more than before. On the other hand, journals on topics of low citation potential generally benefited and stood out, as FNCSI focuses more on the central tendency of the citation distribution, downplays the tails, and compares journal influence based on publication topic.

From a journal editor's perspective, another apparent change brought about by the FNCSI is the encouragement of competition. Unlike the IF, which only involves a single party, the FNCSI, by definition, accentuates one journal's superiority over another. As Eq. (4) demonstrates, the coefficient of weight is 0.5 when two selected items have the same number of citations but doubles when one outnumbers the other. This embeds emphasis clearly and intrinsically on outperforming other journals in the same field.

One could argue that competitiveness is embedded in the IF calculation but, with the definition of FNCSI, the journal ranking competition to claim a topic has never been as intense. Furthermore, as t is a finite set of predefined research topics, the need to “claim a territory” has been more pressing. If a journal consistently publishes highly cited articles with similar keywords, its likelihood of winning against another journal on a specific research topic will increase significantly. Likewise, identifying the predefined terms in t, aligning the journal keywords with them, and better sorting new submissions under the prescribed categories will most likely improve a journal's FNCSI, hence its CAS ranking.

Furthermore, comprehensive journals that publish both research articles and review papers are now being directly compared to review-only journals in the FNCSI calculation based on the same article type. This change suggests that comprehensive journals should pay extra attention to the quality of their review papers: some review papers may seem to have higher citations than regular papers but can compare unfavorably against other review papers to hurt the journal. Maintaining a selective pool for top-tier review papers is critical for the FNCSI assessment.

The reformed CAS system also proposed the Top status for each Major Category to identify outperforming journals in addition to the FNCSI-based tier divisions. A journal must meet one of the following criteria to be considered Top status:

  1. Qualify for Tier 1 of any Major Category.

  2. Qualify for Tier 2 of any Major Category, in the top 10% of two-year total citation.

  3. Passing the collective examination of the Chinese academic community if ranking based on quantitative indices is insufficient (since 2015).

  4. Qualify for Tier 1 of any Minor Category (since 2016).

The idea of a Top journal is to incorporate qualitative assessment into statistical quantification, allowing for flexibility and accommodating high-impact journals of underrepresented research disciplines. Although the Top status has less weight than a Tier 1 status (and often considered as an ancillary qualification), Tier 2 Top journals are certainly the most viable candidates for promotions into Tier 1. The Top status is based on expert opinions, so even if a journal meets one or several of the aforenoted criteria, the qualification is still not guaranteed, which leaves room for bias.

Physics of Fluids has been included in the Physics (物理) Major Category in the Basic edition since 2015. However, following the release of the Advanced edition in 2019, the journal was reclassified under the Engineering and Technology (工程技术 or E&T) Major Category. As there is a significant difference in the number of journals between these two categories (see Table IV), only the ranking percentile can be used to compare meaningfully, before versus after the reform. From 2015 to 2023, Physics of Fluids experienced a significant increase in both popularity and impact.6,7

Despite the significant increase in the number of journals, the recategorization of Physics of Fluids from Physics to E&T impacted minimally the journal's percentile standing in the Basic edition, as shown in Table IV. However, the transition from the Basic edition to the Advanced edition proved pivotal to Physics of Fluids ranking. During the three-year transition phase between 2019–2021, Physics of Fluids rank improved by 43%, 68%, and 61% between 2019, 2020, and 2021, respectively. These improvements are attributable solely to the system switch (see Table V).

TABLE IV.

Statistics of Physics of Fluids and Journal of Fluid Mechanics in the CAS Basic edition in 2015–2021.

Basic Edition (based on IF)
Year Total in Cat. Tier 1 Thresh. Percentile Physics of Fluids Journal of Fluid Mechanics Remark
3-year IF Tier Rank Perc. 3-year IF Tier Rank Perc.
2015  343  17  95.0%  2.0040  94  72.6%  2.2870  74  78.4%  Physics 
2016  345  27  92.2%  2.0290  107  69.0%  2.3970  76  78.0%  Physics 
2017  343  29  91.5%  2.0930  106  69.1%  2.5730  73  78.7%  Physics 
2018  344  28  91.9%  2.1760  107  68.9%  2.7430  70  79.7%  Physics 
2019  1956  126  93.6%  2.3790  622  68.2%  2.9500  444  77.3%  E&T 
2020  2012  129  93.6%  2.8070  596  70.4%  3.1210  513  74.5%  E&T 
2021  2058  142  93.1%  3.2210  622  69.8%  3.3660  585  71.6%  E&T 
Basic Edition (based on IF)
Year Total in Cat. Tier 1 Thresh. Percentile Physics of Fluids Journal of Fluid Mechanics Remark
3-year IF Tier Rank Perc. 3-year IF Tier Rank Perc.
2015  343  17  95.0%  2.0040  94  72.6%  2.2870  74  78.4%  Physics 
2016  345  27  92.2%  2.0290  107  69.0%  2.3970  76  78.0%  Physics 
2017  343  29  91.5%  2.0930  106  69.1%  2.5730  73  78.7%  Physics 
2018  344  28  91.9%  2.1760  107  68.9%  2.7430  70  79.7%  Physics 
2019  1956  126  93.6%  2.3790  622  68.2%  2.9500  444  77.3%  E&T 
2020  2012  129  93.6%  2.8070  596  70.4%  3.1210  513  74.5%  E&T 
2021  2058  142  93.1%  3.2210  622  69.8%  3.3660  585  71.6%  E&T 
TABLE V.

Statistics of Physics of Fluids and Journal of Fluid Mechanics in the CAS Advanced edition in 2019–2023.

Advanced Edition (based on FNCSI)
Year Total in Cat. Tier 1 Thresh. Percentile Physics of Fluids Journal of Fluid Mechanics Remark
FNCSI Tier Rank Perc. FNCSI Tier Rank Perc.
2019  1121  113  89.9%  N.A.  202  82.0%  N.A.  128  88.6%  E&T 
2020  1156  106  90.8%  N.A.  111  90.4%  N.A.  116  90.0%  E&T 
2021  1163  107  90.8%  N.A.  138  88.1%  N.A.  125  89.3%  E&T 
2022  1183  120  89.9%  N.A.  160  86.5%  N.A.  182  84.6%  E&T 
2023  1032  103  90.0%  N.A.  142  86.2%  N.A.  183  82.3%  E&T 
Advanced Edition (based on FNCSI)
Year Total in Cat. Tier 1 Thresh. Percentile Physics of Fluids Journal of Fluid Mechanics Remark
FNCSI Tier Rank Perc. FNCSI Tier Rank Perc.
2019  1121  113  89.9%  N.A.  202  82.0%  N.A.  128  88.6%  E&T 
2020  1156  106  90.8%  N.A.  111  90.4%  N.A.  116  90.0%  E&T 
2021  1163  107  90.8%  N.A.  138  88.1%  N.A.  125  89.3%  E&T 
2022  1183  120  89.9%  N.A.  160  86.5%  N.A.  182  84.6%  E&T 
2023  1032  103  90.0%  N.A.  142  86.2%  N.A.  183  82.3%  E&T 

Such improvements were not unique to Physics of Fluids (POF); the switch benefited most fluids journals. A statistical comparison of the Journal of Fluid Mechanics (JFM) supports this notion, as its ranking improved by at least 10% in absolute percentile for all three overlapping years of the Basic and Advanced editions. We choose the Journal of Fluid Mechanics, being iconic, as our benchmark. We use its statistics to assess Physics of Fluids performance in the forthcoming analysis. Physics of Fluids and Journal of Fluid Mechanics are equally well established, respectively, since 1958 and 1957.

Next, Fig. 1 depicts the percentiles of the Tier 1 threshold, Physics of Fluids, and Journal of Fluid Mechanics in the CAS Basic edition from 2015 to 2021. The Tier 1 percentile threshold remained at a strict 95% in 2015 and earlier years but decreased by several percentages in subsequent years, indicating a trend of decreasing difficulty. Nevertheless, the Physics of Fluids percentile hovered around 70% throughout the seven years with no significant change. Journal of Fluid Mechanics has led Physics of Fluids throughout but saw an apparent and consistent decline after 2018.

FIG. 1.

Percentile of Tier 1 threshold, Physics of Fluids, and Journal of Fluid Mechanics in the CAS Basic edition in 2015–2021.

FIG. 1.

Percentile of Tier 1 threshold, Physics of Fluids, and Journal of Fluid Mechanics in the CAS Basic edition in 2015–2021.

Close modal

While the Advanced edition is a universal game-changer for fluid journals in terms of absolute increase in percentile, Physics of Fluids performance metric differed significantly from the Basic edition. Figure 2 depicts the percentiles of the E&T Tier 1 threshold, Physics of Fluids, and Journal of Fluid Mechanics in the CAS Advanced edition from 2019 to 2023. Notably, between 2019 and 2020, Physics of Fluids experienced a dramatic increase of 8.4%—the most remarkable improvement in its CAS history. However, Physics of Fluids ranking declined steadily thereafter, dropping by 4.2% as of 2023.

FIG. 2.

Percentile of Tier 1 threshold, Physics of Fluids, and Journal of Fluid Mechanics in the CAS Advanced edition in 2019–2023.

FIG. 2.

Percentile of Tier 1 threshold, Physics of Fluids, and Journal of Fluid Mechanics in the CAS Advanced edition in 2019–2023.

Close modal

In the Basic edition, despite its three-year IF unilaterally increasing from 2015 to 2021, its percentile ranking decreased after 2018, indicating that its IF growth is slower than the average of E&T journals after 2018. Nonetheless, in the Advanced edition, its standing improved from 2019 to 2020. This suggests that the FNCSI system favors the likely underrepresented fluids journals, whose IF increase may trail their other E&T peers.

Neither Physics of Fluids nor Journal of Fluid Mechanics have ever made it into Tier 1 of any CAS Major Category. In fact, of all the 34–35 journals under the Physics, Fluids & Plasma Minor Category, only Annual Review of Fluid Mechanics (ARFM) and Nuclear Fusion consistently qualified for Major Category Tier 1 in all five years of the Advanced edition (see Table VI). The former is categorized under E&T and the latter under the Physics and Astrophysics Major Category. Plasma Sources Science & Technology also made it into Tier 1 of Physics and Astrophysics in 2019 and 2022, twice in five years. Figure 3 presents a Venn diagram to deepen the reader's understanding of the Major and Minor Categories specifically with respect to fluids journals.

TABLE VI.

Ranking details of selected fluids journals in the CAS Advanced edition in 2019–2023.

Annu. Rev. Fluid. Mech. Nucl. Fusion Plasma Sources Sci. T. Phys. Fluids J. Fluid Mech.
Major Cat. Tier  Year  E&T  Phys. & Astrophys.  Phys. & Astrophys.  E&T  E&T 
2019 
2020 
2021 
2022 
2023 
Minor Cat. Tier  Year  Physics, Fluid & Plasma 
2019 
2020 
2021 
2022 
2023 
Top Status  Year   
2019  Yes  Yes  Yes  Yes  Yes 
2020  No 
2021  Yes 
2022 
2023  No  No 
Annu. Rev. Fluid. Mech. Nucl. Fusion Plasma Sources Sci. T. Phys. Fluids J. Fluid Mech.
Major Cat. Tier  Year  E&T  Phys. & Astrophys.  Phys. & Astrophys.  E&T  E&T 
2019 
2020 
2021 
2022 
2023 
Minor Cat. Tier  Year  Physics, Fluid & Plasma 
2019 
2020 
2021 
2022 
2023 
Top Status  Year   
2019  Yes  Yes  Yes  Yes  Yes 
2020  No 
2021  Yes 
2022 
2023  No  No 
FIG. 3.

A Venn diagram showing top ranked fluids journals overlapping in different Major and Minor Categories in the Advanced edition in 2023.

FIG. 3.

A Venn diagram showing top ranked fluids journals overlapping in different Major and Minor Categories in the Advanced edition in 2023.

Close modal

In 2021, E&T contained 1163 journals, and Physics and Astrophysics contained only 320 journals, but the corresponding Tier 1 threshold percentiles were 90.8% and 91.6%, respectively. So the difficulty of placing Tier 1 is roughly the same. Even so, CAS has already given its perspective on the different natures of the three journals by putting them in two separate Major Categories. To this end, ARFM is the only Tier 1 non-plasma fluids journal, even though it is a by-invitation-only journal publishing only about 20 papers a year.

Another interesting observation is that there are usually three journals in Tier 1 of the Physics, Fluids & Plasma Minor Category (five in 2023): Physics of Fluids was third in 2020, second in 2022, and third in 2023. However, even being the second-best journal of a Minor Category is still insufficient to rise above the fierce competition in E&T and qualify for Major Category Tier 1. By contrast, the closest Journal of Fluid Mechanics has ever come is fourth place, not once making Tier 1 of the Minor Category.

Year 2023 is the first-ever year that Physics of Fluids failed to be granted the Top status. Knowing that it falls under Tier 1 of the Physics, Fluids & Plasma Minor Category, Physics of Fluids meets at least one of the consideration criteria. Thus, we can attribute this to qualitative evaluation rather than journal performance. Journal of Fluid Mechanics has been given Top status in all five years of the Advanced edition.

To assess the road ahead for Physics of Fluids and Journal of Fluid Mechanics to reach E&T Tier 1, Figs. 4 and 5 plot the percentage below the Tier 1 threshold in the Basic and Advanced editions. In the eight years of the Basic edition, Physics of Fluids was consistently 22%–25% below the threshold with fluctuations but no apparent improvement. Journal of Fluid Mechanics came as close as 12.2% in 2018 but dropped consistently thereafter with its most significant margin of 21.5% in 2021, the year of discontinuation of the Basic edition. The chance of either journal making E&T Tier 1 was slim in the Basic edition.

FIG. 4.

Percent below the CAS Basic edition Tier 1 threshold of Physics of Fluids and Journal of Fluid Mechanics in 2015–2021.

FIG. 4.

Percent below the CAS Basic edition Tier 1 threshold of Physics of Fluids and Journal of Fluid Mechanics in 2015–2021.

Close modal
FIG. 5.

Percent below the CAS Advanced edition Tier 1 threshold of Physics of Fluids and Journal of Fluid Mechanics in 2019–2023.

FIG. 5.

Percent below the CAS Advanced edition Tier 1 threshold of Physics of Fluids and Journal of Fluid Mechanics in 2019–2023.

Close modal

We find that the Advanced edition favors fluids journals. In 2019, the first year of the Advanced edition, the Physics of Fluids 25% margin shrank to 7.9% compared to the Basic edition. Only one year later, Physics of Fluids was its closest ever to Tier 1, falling only 0.4% and five places short of the threshold. The 7.5% improvement from the year before was dramatic, yet it corresponded to only a slight IF increase from 3.514 to 3.521 between 2019 and 2020. One may attribute the CAS ranking improvement to the sharp IF boost of 0.887 (from 2.627 to 3.514) the year before, between 2018 and 2019. However, as Physics of Fluids recorded the greatest IF rise, 1.459, ever in its history (from 3.521 to 4.980) between 2020 and 2021, its margin to Tier 1 even increased by 0.7% in 2022. This observation reinforces the FNCSI indifference to IF.

In comparison, Journal of Fluid Mechanics is experiencing a steady decline. In 2020, Journal of Fluid Mechanics fell only 0.8% and ten places short of the E&T Tier 1 threshold, but its percentile since dropped to 7.7%. Figure 6 shows the percentile difference between Journal of Fluid Mechanics and Physics of Fluids in the Basic and Advanced editions, where a positive value indicates a Journal of Fluid Mechanics lead on Physics of Fluids. Journal of Fluid Mechanics led Physics of Fluids for all seven years of the Basic edition, though the difference had been steadily shrinking following an inflection in 2018. In the Advanced edition, between 2019 and 2021, Journal of Fluid Mechanics has twice led Physics of Fluids and only once fell behind by just 0.4%. For unknown reasons, after 2022, Journal of Fluid Mechanics trailed Physics of Fluids with increasingly expanding gaps, reaching a deficit of 3.9% in 2023—the largest ever in the Advanced edition. Considering its 6.6% lead over Physics of Fluids in 2019, the Journal of Fluid Mechanics net decline is as large as 10.5% over the five-year period.

FIG. 6.

Net percentile difference of Journal of Fluid Mechanics versus Physics of Fluids in the CAS Basic and Advanced editions in 2015–2023.

FIG. 6.

Net percentile difference of Journal of Fluid Mechanics versus Physics of Fluids in the CAS Basic and Advanced editions in 2015–2023.

Close modal

This paper analyzes the Chinese Academy of Science journal ranking system from 2015 to 2023 with a particular focus on the standings of Physics of Fluids. Based on official statistics, Physics of Fluids has risen in the CAS system. This improvement is attributable to its increasing popularity and quality, particularly pronounced after the CAS reforms in 2019 involving the Advanced edition and Field Normalized Citation Success Index.

The CAS adopts arbitrarily the roughly pyramidal distribution of Ref. 4; it would be instructive to explore other distributions, including Gaussian, for instance. We leave this intriguing work for another day.

Despite Physics of Fluids being one of the only four journals ever to make Tier 1 in the Physics, Fluid & Plasma Minor Category since 2019, it has yet to make Tier 1 in the Engineering & Technology Major Category. In the most recent CAS report, Physics of Fluids has outperformed the fluid mechanics icon, Journal of Fluid Mechanics, standing as the most likely candidate for second-ever Tier 1 status in Engineering & Technology after the Annual Review of Fluid Mechanics. If so, Physics of Fluids would also be the first journal that is neither by-invitation-only nor restricted to plasma fluids to enter this classification.

This research was undertaken, in part, thanks to support from the Canada Research Chairs program of the Government of Canada for the Natural Sciences and Engineering Research Council of Canada (NSERC) Tier 1 Canada Research Chair in Physics of Fluids, the National Natural Science Foundation of China (Project No. HW2023001), the Supporting Scheme of Chongqing for Returned Overseas Chinese Entrepreneurial Start-ups (Project No. cx2023004), the Start-Up Fund of Chongqing University (Project Nos. 02180011080006 and 0218005203008), and the Fundamental Research Fund of Central Universities of Chongqing University (Project No. 0218005203003).

The authors declare that they have no conflict of interest.

All authors contributed to the conception of the work. Funding, management, and supervision were led by Cruz Y. Li. Material preparation, data collection, and formal analysis were led by Cruz Y. Li, assisted by Yunlong Wang, and Alan Jeffrey Giacomin. The first draft of the manuscript was written by Cruz Y. Li. All authors commented on previous versions of the manuscript. The revision was led by Alan Jeffrey Giacomin and assisted by Cruz Y. Li. All authors read, contributed to, and approved the final manuscript.

The datasets generated or analyzed during the current work are restricted by provisions of the funding source but are available from the corresponding author on reasonable request.

1.
JCR Ranking - Journal Citation Reports. Clarivate. Available online at https://www.jcr.clarivate.com.
2.
中国科学院文献情报中心期刊分区表 (Journal Ranking List of Publication Information Center of Chinese Academy of Science). Available online at https://www.fenqubiao.com.
3.
S.
Tong
,
F.
Chen
,
L.
Yang
, and
Z.
Shen
, “
Novel utilization of a paper-level classification system for the evaluation of journal impact: An update of the CAS Journal Ranking
,”
Quant. Sci. Stud.
4
(
4
),
960
975
(
2023
).
4.
B.
Jin
and
S.
Wang
, “
SCI期刊等级区域的划分及其中国论文的分布 (The division of SCI journal grades and the distribution of Chinese papers)
,”
Sci. Res. Manage.
20
(
2
),
1
7
(
1999
).
5.
N.
Phan-Thien
and
A. J.
Giacomin
, “
Growth-adjusted Impact Factor
,”
Phys. Fluids
36
,
050402
(
2024
).
6.
A. J.
Giacomin
, “
Inaugural Editorial: Strengths of a Fluids Publishing Gem
,”
Phys. Fluids
28
,
010401
(
2016
).
7.
A. J.
Giacomin
, “
Editorial: The Four Ships of Physics of Fluids
,”
Phys. Fluids
28
,
020401
(
2016
).