Numerical study of laminar and turbulent flows inside a turnaround duct with and without guide vanes

1987 ◽  
Author(s):  
S.-J. LIN ◽  
JAMES CHANG
Keyword(s):  
Turbulent Flows ◽  
Numerical Study ◽  
Guide Vanes ◽  
Laminar And Turbulent Flows

A numerical study on combined baffles quick-separation device

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ehsan Dehdarinejad ◽  
Morteza Bayareh ◽  
Mahmud Ashrafizaadeh
Keyword(s):  
Turbulent Flows ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Turbulence Models ◽  
Complete Separation ◽  
Solid Particles ◽  
Flow Rates ◽  
Separation Device ◽  
Coupling Technique ◽  
Laminar And Turbulent Flows

Abstract The transfer of particles in laminar and turbulent flows has many applications in combustion systems, biological, environmental, nanotechnology. In the present study, a Combined Baffles Quick-Separation Device (CBQSD) is simulated numerically using the Eulerian-Lagrangian method and different turbulence models of RNG k-ε, k-ω, and RSM for 1–140 μm particles. A two-way coupling technique is employed to solve the particles’ flow. The effect of inlet flow velocity, the diameter of the splitter plane, and solid particles’ flow rate on the separation efficiency of the device is examined. The results demonstrate that the RSM turbulence model provides more appropriate results compared to RNG k-ε and k-ω models. Four thousand two hundred particles with the size distribution of 1–140 µm enter the device and 3820 particles are trapped and 380 particles leave the device. The efficiency for particles with a diameter greater than 28 µm is 100%. The complete separation of 22–28 μm particles occurs for flow rates of 10–23.5 g/s, respectively. The results reveal that the separation efficiency increases by increasing the inlet velocity, the device diameter, and the diameter of the particles.

Analysis of Turbulent Flow in 180° Turning Ducts With and Without Guide Vanes

2007 ◽  
Author(s):  
Jiang Luo ◽  
Eli H. Razinsky
Keyword(s):  
Turbulent Flows ◽  
Cross Section ◽  
Flow Separation ◽  
Pressure Loss ◽  
Numerical Study ◽  
Guide Vane ◽  
Outer Wall ◽  
Loss Reduction ◽  
Guide Vanes ◽  
Curvature Effects

This paper presents a numerical study of the turbulent flows through a number of 2-D and 3-D 180° U-ducts, with and without guide vanes, using the Reynolds-averaged Navier-Stokes method. Computations have been first carried out for a 2-D U-duct flow (W/H = 1.0) with four turbulence models (V2F, k-ε, SST and Reynolds stress). The models’ capability for streamline curvature effects on turbulence and separation has been assessed, using flow and turbulence data. The effects of adding a guide vane inside the bend have been analyzed, to reduce/avoid flow separation. Three vanes with different radial locations have been studied, and the mechanism for pressure loss reduction has been examined. Analyses have been performed for turbulent flows in 3-D U-ducts with square cross-section and sharp 180° turning (W/D = 0.2), similar to the U-bends in typical turbine blade cooling passages. The predictions are compared with the data of outer wall pressure. The effects of the guide vane and outer-wall shape on the flow separation, secondary-flow vortices and pressure loss have been evaluated. The combined vane and uniform cross-section area provide a large benefit for the flow distribution and pressure loss reduction.

Analysis of Turbulent Flow in 180 deg Turning Ducts With and Without Guide Vanes

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Jiang Luo ◽  
Eli H. Razinsky
Keyword(s):  
Turbulent Flows ◽  
Cross Section ◽  
Flow Separation ◽  
Pressure Loss ◽  
Numerical Study ◽  
Guide Vane ◽  
Outer Wall ◽  
Duct Flow ◽  
Guide Vanes ◽  
Curvature Effects

This paper presents a numerical study of the turbulent flows through a number of 2D and 3D 180 deg U-ducts, with and without guide vanes, using the Reynolds-averaged Navier–Stokes method. Computations have been first carried out for a 2D U-duct flow (W/H=1.0) with four turbulence models (V2F, k-ε, shear stress transport (SST), and Reynolds stress). The models’ capability for predicting streamline curvature effects on turbulence and separation has been assessed, using flow and turbulence data. The effects of adding a guide vane inside the bend have been analyzed to reduce/avoid flow separation. Three vanes with different radial locations have been studied, and the mechanism for pressure loss reduction has been examined. Analyses have been performed for turbulent flows in 3D U-ducts with square cross section and sharp 180 deg turning (W/D=0.2), similar to the U-bends in typical turbine blade cooling passages. The predictions are compared with the data of outer-wall pressure. The effects of the guide vane and outer-wall shape on the flow separation, secondary-flow vortices, and pressure loss have been evaluated. The combined vane and uniform cross section area are found to improve the flow distribution and reduce the pressure loss significantly.

A Numerical Study of Laminar and Turbulent Heat Transfer in a Periodically Corrugated Wall Channel

1985 ◽  
Vol 107 (3) ◽  
pp. 564-569 ◽  
Author(s):  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Solution Method ◽  
Numerical Study ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Complex Flow ◽  
Flow Phenomena ◽  
Corrugated Wall ◽  
Laminar And Turbulent Flows

A numerical study is reported on hydrodynamic and heat transfer characteristics in a periodically corrugated wall channel for both laminar and turbulent flows. For turbulent flows the k-ε turbulence model with a refined near-wall model is adopted for the computation of the flow field for step ratios H/W ranging from two to four. The Reynolds number considered in this study varies from 10 to 25,000. The solution method of the governing transport equations is based on the modified hybrid scheme. As a result of extensive computations, the complex flow patterns in the perpendicularly corrugated wall channel are clarified and the mechanisms of heat transfer are explained relating to the flow phenomena of separation, deflection, recirculation, and reattachment. Finally it was observed that the effect of the step ratio on the local Nusselt number is minor. Moreover, it was found that both skin friction and heat transfer patterns change drastically from laminar to turbulent flows.

scholarly journals Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1079
Author(s):  
Lena Mahl ◽  
Patrick Heneka ◽  
Martin Henning ◽  
Roman B. Weichert
Keyword(s):  
Boundary Conditions ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Free Water ◽  
Lateral Wall ◽  
Lateral Spreading ◽  
Propagation Length ◽  
Vertical Slot ◽  
Surface Jets

The efficiency of a fishway is determined by the ability of immigrating fish to follow its attraction flow (i.e., its jet) to locate and enter the fishway entrance. The hydraulic characteristics of fishway entrance jets can be simplified using findings from widely investigated surface jets produced by shaped nozzles. However, the effect of the different boundary conditions of fishway entrance jets (characterized by vertical entrance slots) compared to nozzle jets must be considered. We investigate the downstream propagation of attraction jets from the vertical slot of a fishway entrance into a quiescent tailrace, considering the following boundary conditions not considered for nozzle jets: (1) slot geometry, (2) turbulence characteristics of the approach flow to the slot, and (3) presence of a lateral wall downstream of the slot. We quantify the effect of these boundary conditions using three-dimensional hydrodynamic-numeric flow simulations with DES and RANS turbulence models and a volume-of-fluid method (VoF) to simulate the free water surface. In addition, we compare jet propagation with existing analytical methods for describing jet propagations from nozzles. We show that a turbulent and inhomogeneous approach flow towards a vertical slot reduces the propagation length of the slot jet in the tailrace due to increased lateral spreading compared to that of a jet produced by a shaped nozzle. An additional lateral wall in the tailrace reduces lateral spreading and significantly increases the propagation length. For highly turbulent flows at fishway entrances, the RANS model tends to overestimate the jet propagation compared to the transient DES model.

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