Special Issue on “CFD Based Researches and Applications for Fluid Machinery and Fluid Device, Volume II”

Computational fluid dynamics (CFD)-based advanced numerical optimization techniques are essential as practical tools used to enhance the performance of various fluid machines and fluid devices for realizing carbon neutrality [1,2,3]. In particular, the demand for these advanced techniques in the industrial engineering field is gradually increasing in efforts to solve complicated unsteady flow phenomena and complex mechanisms such as unsteady flow instability, conjugate heat transfer, fluid-induced vibration, rotor–stator interaction, surging and choking phenomena, cavitation, noise, and so on [4,5,6].

Based on the previous Special Issue on published in Processes [7], this second Special Issue, “CFD Based Researches and Applications for Fluid Machinery and Fluid Device, Volume II”, explores topics related to the latest advanced CFD techniques and applications of various fluid machines and devices in the industrial engineering fields. The twelve papers published in this second Special Issue focus especially on advancements in advanced CFD techniques for designing and analyzing various fluid machines, as indicated in the following list of contributions and brief summaries below:

• Ahn, J.; Song, J.C.; Lee, J.S. Large Eddy Simulation of Conjugate Heat Transfer in a Ribbed Channel: Reynolds Number Effect. Processes 2022, 10, 1928. https://doi.org/10.3390/pr10101928
• Siddappaji, K.; Turner, M.G. An Advanced Multifidelity Multidisciplinary Design Analysis Optimization Toolkit for General Turbomachinery. Processes 2022, 10, 1845. https://doi.org/10.3390/pr10091845
• Chen, Z.; Yang, H.; Wei, Y.; He, H.; Zhang, C.; Nie, T.; Yu, P.; Zhang, W. Effect of a Radially Offset Impeller on the Unsteady Characteristics of Internal Flow in a Double-Suction Centrifugal Fan. Processes 2022, 10, 1604. https://doi.org/10.3390/pr10081604
• Wang, H.; Yang, S.; Lu, T. Performance-Matching Optimization Design of Loader-Hydraulic System Based on Hydrodynamics Analysis. Processes 2022, 10, 1524. https://doi.org/10.3390/pr10081524
• Xu, L.; Lv, F.; Li, F.; Ji, D.; Shi, W.; Lu, W.; Lu, L. Comparison of Energy Performance of Shaft Tubular Pump Device at Two Guide Vane Inlet Angles. Processes 2022, 10, 1054. https://doi.org/10.3390/pr10061054
• Je, Y.-W.; Lee, J.-C.; Kim, Y.-J. Performance Characteristics of In-Line Oil Separator with Various Airfoil Vane Configurations of the Axial-Flow Swirl Generator. Processes 2022, 10, 948. https://doi.org/10.3390/pr10050948
• Shrestha, U.; Choi, Y.-D. Estimation of Reverse Flow Rate in J-Groove Channel of AJP and SCP Models Using CFD Analysis. Processes 2022, 10, 785. https://doi.org/10.3390/pr10040785
• Je, Y.-W.; Kim, Y.-J.; Kim, Y.-J. The Prediction of Separation Performance of an In-Line Axial Oil–Water Separator Using Machine Learning and CFD. Processes 2022, 10, 375. https://doi.org/10.3390/pr10020375
• Yue, D.; Li, L.; Wei, L.; Liu, Z.; Liu, C.; Zuo, X. Effects of Pulse Voltage Duration on Open–Close Dynamic Characteristics of Solenoid Screw-In Cartridge Valves. Processes 2021, 9, 1722. https://doi.org/10.3390/pr9101722
• Huang, B.; Zeng, G.; Qian, B.; Wu, P.; Shi, P.; Qian, D. Pressure Fluctuation Reduction of a Centrifugal Pump by Blade Trailing Edge Modification. Processes 2021, 9, 1408. https://doi.org/10.3390/pr9081408
• Guo, T.; Zhang, J.; Luo, Z. Analysis of Channel Vortex and Cavitation Performance of the Francis Turbine under Partial Flow Conditions. Processes 2021, 9, 1385. https://doi.org/10.3390/pr9081385
• Huang, B.; Guo, M.; Lu, B.; Wu, Q.; Zuo, Z.; Liu, S. Geometric Optimization of an Extracorporeal Centrifugal Blood Pump with an Unshrouded Impeller Concerning Both Hydraulic Performance and Shear Stress. Processes 2021, 9, 1211. https://doi.org/10.3390/pr9071211

Ahn et al. (contribution 1) performed conjugate heat-transfer-based large eddy simulation (LES) for analyzing the detailed ribbed channel in the internal cooling passage of a gas turbine. Siddappaji and Turner’s article (contribution 2) investigates a comprehensive framework on multifidelity, multidisciplinary design analysis optimization combined with advanced CFD techniques for various axial and radial turbomachines. The effect of a radially offset impeller on the unsteady aerodynamic performance and characteristics of the internal flow in a double-suction centrifugal fan was analyzed systematically in the study conducted by Chen et al. (contribution 3) based on unsteady Reynolds-averaged Navier–Stokes (RANS) simulations. Wang et al. (contribution 4) carried out the performance-matching optimization design of a loader hydraulic system through special hydrodynamic analysis. In the fifth article, Xu et al. (contribution 5) numerically compare and structurally analyze the energy performance of a shaft tubular pump device with two guide vane inlet angles using CFD techniques based on RANS equations.

Je et al. (contribution 6) numerically calculated the performance characteristics of an in-line oil separator with various airfoil vane configurations of the axial-flow swirl generator. In their work, Shrestha and Choi (contribution 7) quantitatively estimated the reverse flow rate in the J-groove channel of an annular jet pump and a screw centrifugal pump model using systematic CFD analysis. A numerical prediction study of the separation performance of an in-line axial oil–water separator with various design variables was conducted by Je et al. (contribution 8) based on machine learning and CFD techniques. To analyze the effect of pulse voltage duration on the open–close dynamic characteristics of solenoid screw-in cartridge valves, Yue et al. (contribution 9) established a detailed simulation model based on mechanical, hydraulic, electromagnetic, and control subjects and verified it through an experimental test.

Moreover, Huang et al. (contribution 10) explored the features of blade-passing frequency excitation with a blade trailing edge modification of a low-specific-speed centrifugal pump from the perspective of local Euler head distribution based on unsteady RANS techniques. In the work of Guo et al. (contribution 11), the LES method based on the wall-adapting local eddy viscosity subgrid-scale stress model with the Schnerr–Sauer cavitation model was employed to carefully analyze the flow and cavitation characteristics in the flow passage of a Francis turbine under partial flow conditions. Finally, Huang et al. (contribution 12) conducted the geometric numerical multi–objective optimization of an extracorporeal centrifugal blood pump with an unshrouded impeller, investigating both their hydraulic performance and shear stress.

As mentioned above, most papers published in this second Special Issue focus specifically on the latest advancements in the advanced CFD techniques for improving the specific performance of various fluid machines and devices. Therefore, these findings of the papers will be practically useful for designing similar fluid machines and devices in the future.

Finally, all the guest editors of this second Special Issue would like to express our gratitude to the Section Managing Editor, Ms. Shirley Wang, for organizing these first and second Special Issues of Processes. In addition, we are also thankful to all the reviewers for their insightful questions and valuable comments that improved the quality of all the papers published in this Special Issue, which is available at https://www.mdpi.com/journal/processes/special_issues/CFD_Fluid_Device_II (accessed on 20 December 2022).