Critical flow regime in a stratified medium

1979 ◽  
Vol 14 (2) ◽  
pp. 289-292
Author(s):  
K. E. Dzhaugashtin
Keyword(s):  
Flow Regime ◽  
Stratified Medium ◽  
Critical Flow ◽  
Critical Flow Regime

scholarly journals The conditions for occurrence of critical flow regime of water in the open stream

2019 ◽  
Vol 97 ◽  
pp. 05006
Author(s):  
Yuliya Bryanskaya ◽  
Aleksandra Ostiakova
Keyword(s):  
Froude Number ◽  
Flow Regime ◽  
Water Flow ◽  
Practical Interest ◽  
Open Water ◽  
Critical Regime ◽  
Critical Flow ◽  
Channel Processes ◽  
Channel Deformations ◽  
Critical Flow Regime

For the solution of engineering problems require increasingly accurate estimates of the hydraulic characteristics of the water streams. To date, it is impossible to consider sufficiently complete theoretical and experimental justification of the main provisions of the theory of turbulence, hydraulic resistance, channel processes. The composition of tasks related to flows in wide channels, turbulence problems are of scientific and practical interest. Various interpretations of the determination of the critical Froude number in wide open water flows based on observations and theoretical transformations are considered. The conditions for the emergence of a critical regime of water flow in an open wide channel are analyzed in order to estimate the critical Froude number and critical depth. Estimates of the critical Froude number for laboratory and field conditions are given. The estimations allow us to consider the proposed approach acceptable for determining the conditions of occurrence of the critical flow regime. The General, physical interpretation of conditions of occurrence of the critical regime of water flow on the basis of phenomenological approach is specified. The results take into account the values of the components of the total specific energy of the section. This shows the estimated calculation. The results obtained theoretically make it possible to compare the above interpretations and determine their applicability, and the results of the analysis can be useful for the estimated calculations of flows in channels and river flows in rigid, undeformable boundaries and with minor channel deformations.

Fluid dynamics around three cylinders in presence of small control cylinders

2020 ◽  
Vol 98 (11) ◽  
pp. 1060-1076
Author(s):  
Ali Ahmed ◽  
Shams-ul Islam ◽  
Chao Ying Zhou ◽  
Raheela Manzoor
Keyword(s):  
Drag Coefficient ◽  
Flow Regime ◽  
Strouhal Number ◽  
Numerical Study ◽  
Critical Flow ◽  
Square Cylinders ◽  
Tandem Square Cylinders ◽  
Critical Flow Regime ◽  
Force Reduction ◽  
Control Cylinder

A numerical study is performed to analyze the effect of small control cylinders on fluid force reduction and vortex shedding suppression on the flow past three inline square cylinders using the lattice Boltzmann method. The Reynolds number Re = 160 is fixed while the spacing between the cylinders is taken in the range of 1.0D ≤ g* ≤ 5.0D (where D is the size of the main cylinder) and the control cylinder size is varied from 0.1D to 0.5D. To systematically understand the effect of control cylinders on the forces, a detailed analysis of Strouhal number (St), mean drag coefficient (CDmean), and root mean square values of the drag and lift coefficients is presented in this paper. In this study, it is observed that the average mean drag coefficient (CDmeanaverage) and Strouhal number reached either maximum or minimum values at different values of separation ratio (g*) and small control cylinder size (d). It is found that at (g*, d) = (5.0, 0.0) and (1.0, 0.5), the average CDmean attains its maximum (CDmeanaverage = 0.7813) and minimum (CDmean = 0.0988) values. Furthermore, at (g*, d) = (5.0, 0.3) and (2.0, 0.0) the average St attains its maximum (St = 0.1780) and minimum (St = 0.041) values. It is found that the flow regimes completely change in the presence of control cylinders. In particular, at g* = 4.0 there is a critical flow regime when the size of the control cylinder changes from 0.1 to 0.5. The sudden jump in the mean drag coefficient and Strouhal number for the middle cylinder with their maximum and minimum values also confirms the critical flow regime. The effect of control cylinders within tandem square cylinders has not been studied before.

scholarly journals Estimation of the nozzle with the stepped divergent section in critical flow regime

2018 ◽  
Vol 1105 ◽  
pp. 012004
Author(s):  
I I Saushin ◽  
N I Mikheev ◽  
A E Goltsman ◽  
D V Kratirov
Keyword(s):  
Flow Regime ◽  
Critical Flow ◽  
Critical Flow Regime

Modeling of Flow Around a Circular Cylinder in Sub-Critical Flow Regime With the Use of Dynamic Grid Adaptation

2002 ◽  
Author(s):  
Govert de With ◽  
Arne E. Holdo̸ ◽  
Thomas A. Huld
Keyword(s):  
Circular Cylinder ◽  
Flow Regime ◽  
Turbulent Viscosity ◽  
Mesh Refinement ◽  
High Rate ◽  
Critical Flow ◽  
Computational Domain ◽  
Grid Adaptation ◽  
High Gradients ◽  
Critical Flow Regime

In the present study a Dynamic Grid Adaptation (DGA) algorithm is used for predicting flow around a circular cylinder in sub-critical flow regime at a Reynolds number of 1.4·105. The reason for adopting a DGA algorithm is to use the flow field as a driving criteria for mesh refinement rather then the geometry of the computational domain or the judgment of the CFD user as common in conventional mesh. It is demonstrated how DGA reduces the mesh size significantly and also makes time consuming mesh testing unnecessary. The concept being adopted is to concentrate mesh refinement in regions with high gradients and high turbulent viscosity, while in the region further downstream where the flow is fully developed a coarser mesh will develop and turbulence is modeled with the Large Eddy Simulation (LES) turbulence model. The aim of the study is to present an appropriate variable for mesh refinement, which accomplishes a high rate of mesh refinement in the region with high gradients. The new variable is a product of the local mesh cell size and the rate of strain and includes two additional variables to allow control over the refinement behaviour.

LOCAL HEAT TRANSFER OF TUBES IN THE CRITICAL FLOW REGIME FOR Pr > 1

1974 ◽  
Author(s):  
Algirdas Zukauskas ◽  
R. Ulinskas ◽  
Juozas Vytautas Ziugzda
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Critical Flow ◽  
Critical Flow Regime

scholarly journals Modern vision for critical flow in an egg-shaped section

2021 ◽  
Author(s):  
Hachemi Rachedi Lamia ◽  
Lakehal Moussa ◽  
Achour Bachir
Keyword(s):  
Froude Number ◽  
Critical Regime ◽  
Critical Flow ◽  
New Approach ◽  
Smooth Channel ◽  
Critical Flow Regime ◽  
Modern Vision ◽  
The One ◽  
Definition Of ◽  
Steep Slopes

Abstract The critical regime plays a primordial role in the study of gradually varying flows by classifying flow regimes and slopes. Through this work, a new approach is proposed to analyze critical flow regime in an egg-shaped channel. Based on both the definition of Froude number and Achour and Bedjaoui general discharge relationship, a relation between critical and normal depths is derived and then graphically represented for the particular case of a smooth channel characterized by a generating diameter equal to one meter. The results show the influence of the slope on the frequency of occurrence of the critical regime. At the same time and independently of the flow rate, a very advantageous approach for the calculation of the Froude number has been proposed. The study shows that there are six zones to differentiate the various flow states, namely: on the one hand for steep slopes two subcritical zones interspersed by a supercritical zone and on the other hand for mild slopes a zone corresponding to uniform flow, an area where the flow is probably gradually varied and finally an area where the flow is abruptly varied. Based on the specific energy equation, a validation process concluded that the proposed relationships were reliable.

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