Creation of a parameterized model of a return channel flow path for CFD-researches

2020 ◽  
Author(s):  
Y. B. Galerkin ◽  
A. F. Rekstin ◽  
L. N. Marenina ◽  
K. V. Soldatova
Keyword(s):  
Channel Flow ◽  
Flow Path ◽  
Parameterized Model ◽  
Return Channel

scholarly journals Rivers in reverse: Upstream-migrating dechannelization and flooding cause avulsions on fluvial fans

Geology ◽  
2021 ◽  
Author(s):  
Douglas A. Edmonds ◽  
Harrison K. Martin ◽  
Jeffery M. Valenza ◽  
Riley Henson ◽  
Gary S. Weissmann ◽  
...  
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Flow Path ◽  
One Dimensional ◽  
Channel Blockage ◽  
Landsat Satellite ◽  
Median Rate ◽  
Floodplain Sedimentation

The process of river avulsion builds floodplains and fills alluvial basins. We report on a new style of river avulsion identified in the Landsat satellite record. We found 69 examples of retrogradational avulsions on rivers of densely forested fluvial fans in the Andean and New Guinean alluvial basins. Retrogradational avulsions are initiated by a channel blockage, e.g., a logjam, that fills the channel with sediment and forces water overbank (dechannelization), which creates a chevron-shaped flooding pattern. Dechannelization waves travel upstream at a median rate of 387 m/yr and last on average for 13 yr; many rivers show multiple dechannelizing events on the same reach. Dechannelization ends and the avulsion is complete when the river finds a new flow path. We simulate upstreammigrating dechannelization with a one-dimensional morphodynamic model for open channel flow. Observations are consistent with model results and show that channel blockages can cause dechannelization on steep (10–2 to 10–3), low-discharge (~101 m3 s–1) rivers. This illustrates a new style of floodplain sedimentation that is unaccounted for in ecologic and stratigraphic models.

scholarly journals Effect of Aspect Ratio and Installation Direction on Channel Flow Heat Transfer Performance under a Wide Range of Reynolds Number

2019 ◽  
pp. 1-12
Author(s):  
Shunichi Sakuragi ◽  
Daisuke Torii
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Channel Flow ◽  
Rectangular Cross Section ◽  
Transfer Characteristic ◽  
Flow Path ◽  
Cooling Fluid ◽  
Wide Range ◽  
The Difference ◽  
Narrow Plate

In recent years, in the cooling technology for high-power electronic devices such as power transistors used for drive motor control of electric vehicles and hybrid vehicles, a method of flowing a cooling fluid to a cooling substrate having a fin structure has become the main technology. The structure of the cooling fluid flow path is a channel flow through multiple narrow plate gaps to secure a heat transfer area. In this study, the heat transfer characteristics when the aspect ratio of the channel having a flat rectangular cross-section was changed were investigated in detail by experiments. Moreover, the difference in the heat transfer characteristic at the time of making a rectangular flow path into vertical installation and horizontal installation was also investigated.

scholarly journals Stator elements optimization of centrifugal compressor intermediate type stage by CFD methods

2020 ◽  
Vol 178 ◽  
pp. 01020 ◽  
Author(s):  
Lyubov Marenina ◽  
Yuri Galerkin ◽  
Alexandr Drozdov
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Rate Coefficient ◽  
Optimization Problems ◽  
Flow Path ◽  
Loss Coefficient ◽  
Radius Of Curvature ◽  
Intermediate Type ◽  
Flow Rate Coefficient ◽  
Return Channel

Optimal gas-dynamic design is a complex and time-consuming process. Modern CFD methods help in solving optimization problems and reliably calculating characteristics of stator elements of centrifugal compressor stages. To carry out such calculations, it is necessary to create a parametrized model, which facilitates automation of the process of changing the flow path geometry, rebuilding its dimensions and the computational grid. Using the Direct Optimization program of the ANSYS software package, we have optimized the flow path of the stator elements of a centrifugal compressor intermediate type stage consisting of a vaneless diffuser and a return channel. In this paper, the MOGA (Multi-Objective Genetic Algorithm) optimization method was used. The object of the study was stator elements of one of the model stages designed by the Problem Laboratory of Compressor Engineering, SPbPU. The goal was to achieve the minimum value of the loss coefficient of stator elements when changing 5 geometric parameters: the number of vanes, the inlet vane angle, the height of the vane at the inlet to the return channel vane cascade, the radius of curvature of the leading edge and the thickness of the vane profile. For the best variants based on the results of optimization, the characteristics of the loss coefficient depending on the flow rate coefficient were calculated, their characteristics were compared with the initial variant of the stator elements. The best variant in the design mode has a loss coefficient 4.4% lower than the reference model. With a flow rate coefficient of 1.63 times greater than the calculated one, the optimized variant’s loss coefficient is 33% less.

Experimental and Numerical Study of Return Channel Flow Influence on Surge Margin of a Multi-Stage Centrifugal Compressor

2015 ◽  
Author(s):  
Yoshifumi Nishida ◽  
Hideo Nishida ◽  
Hiromi Kobayashi ◽  
Takahiro Nishioka
Keyword(s):  
Channel Flow ◽  
Centrifugal Compressor ◽  
Swirl Flow ◽  
Velocity Difference ◽  
Flow Angle ◽  
Blade Loading ◽  
Second Stage ◽  
Surge Margin ◽  
Multi Stage ◽  
Return Channel

Experimental and numerical studies were performed to investigate influences of the return channel flow on the surge margin of a multistage centrifugal compressor. Two return channels, which were named RCH-A and RCH-B, were designed and evaluated in a two-stage centrifugal compressor. The measured performance of the compressor suggested that the surge margin of this compressor was dominated by the operating limit of the second stage and that the surge margin of RCH-B was 5% larger than that of RCH-A. The outlet flow of RCH-A and RCH-B swirled in a counter-rotating direction near the shroud region, and the flow angle at the outlet of RCH-A was larger than that of RCH-B. CFD was conducted to investigate the internal flow in the return channel. The CFD results of both RCH-A and RCH-B showed that the flow separation occurred on the suction surface of the return vanes near the operating limit. This separation induced the velocity difference between the suction and pressure sides, and the swirl flow in the counter-rotating direction was generated by this velocity difference. The swirl flow in the counter-rotating direction increased the blade loading of the second stage impeller at the operating limit. It was considered that the blade loading of RCH-B was lower than that of RCH-A at the operating limit, because the swirl flow in the counter-rotating direction of RCH-B was weaker than that of RCH-A. Therefore, the surge margin of the second impeller with RCH-B seemed to be larger than that with RCH-A. It was conclude from the experimental and numerical results that the locally swirl flow in the counter-rotating direction at the outlet of the return channels near the shroud side influenced the surge margins of the downstream impeller and the multi-stage centrifugal compressor.

Optimization of Return Channels of High Flow Centrifugal Compressor Stages by CFD-Methods

2021 ◽  
pp. 49-64
Author(s):  
L.N. Marenina ◽  
Y.B. Galerkin
Keyword(s):  
Centrifugal Compressor ◽  
Loss Factor ◽  
Optimization Method ◽  
Flow Path ◽  
Flow Coefficient ◽  
Algorithm Optimization ◽  
Minimum Loss ◽  
Direct Optimization ◽  
Modern Computer ◽  
Parameterized Model

Calculations performed with modern computer fluid dynamics (CFD) programs aid in optimizing the flow path of a centrifugal compressor. The characteristics of the stator elements of the flow path, calculated by CFD methods, are considered to be quite accurate. Optimization of three-stage reverse-directing devices with a large flow rate (0.15) and different theoretical head coefficients (0.45; 0.60; 0.70) has been carried out. For optimizing return channels a parameterized model was created. Optimization was performed with MOGA (Multi-Objective Genetic Algorithm) optimization method in the Direct Optimization program of the ANSYS software package. The optimization goal was to achieve the minimum loss factor at the design point. In the optimization process, the following parameters were varied: the number of and the inlet angle of the vanes, the height of the vanes at the inlet, external and internal radii of curvature of the U-bend. For the return channel with a minimum loss coefficient, the dependences of this parameter on the flow coefficient were calculated. Comparison with the characteristics of the initial variant showed that the optimized return channels are more efficient over the entire flow range. Optimization allowed reducing the loss factor by 20%.

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