scholarly journals Numerical Investigation on Fluid Flow in a 90-Degree Curved Pipe with Large Curvature Ratio

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Yan Wang ◽  
Quanlin Dong ◽  
Pengfei Wang
Keyword(s):  
Fluid Flow ◽  
Internal Flow ◽  
Fluid Flows ◽  
Detached Eddy Simulation ◽  
Number Range ◽  
Curvature Ratio ◽  
Large Curvature ◽  
Curved Pipe ◽  
Eddy Simulation ◽  
Curved Pipes

In order to understand the mechanism of fluid flows in curved pipes, a large number of theoretical and experimental researches have been performed. As a critical parameter of curved pipe, the curvature ratioδhas received much attention, but most of the values ofδare very small (δ<0.1) or relatively small (δ≤0.5). As a preliminary study and simulation this research studied the fluid flow in a 90-degree curved pipe of large curvature ratio. The Detached Eddy Simulation (DES) turbulence model was employed to investigate the fluid flows at the Reynolds number range from 5000 to 20000. After validation of the numerical strategy, the pressure and velocity distribution, pressure drop, fluid flow, and secondary flow along the curved pipe were illustrated. The results show that the fluid flow in a curved pipe with large curvature ratio seems to be unlike that in a curved pipe with small curvature ratio. Large curvature ratio makes the internal flow more complicated; thus, the flow patterns, the separation region, and the oscillatory flow are different.

Detached Eddy Simulation for Model Hydro Turbine

2006 ◽  
Author(s):  
Xiaojing Wu ◽  
Shuhong Liu ◽  
Yulin Wu
Keyword(s):  
Vortex Motion ◽  
Internal Flow ◽  
Simulation Method ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Complex Flow ◽  
Hydro Turbine ◽  
Eddy Simulation ◽  
Mesh Density ◽  
Flow Vortex

In this paper, detached eddy simulation method is applied to the numerical simulation for whole passage of a model hydro turbine. The method combines the strong points of Reynolds-averaged Navier-Stokes and Large eddy simulation. In this model, Spalart–Allmaras turbulent model is improved, which reduces to a RANS formulation near a solid surface and to a subgrid model away from the wall. The hexahedron type mesh is used to divide the model, which can decrease the mesh scale and computation cost. In this paper, a unsteady turbulent simulation is done for model hydro turbine with this viscous model. The internal flow, vortex motion and pressure fluctuation inside hydro turbine can be studied from the result, which are also compared with the experiment data. It can be seen that this method can describe the complex flow of the turbine well while the mesh density is not very high.

scholarly journals Hybrid Numerical Simulation of Jet Blast Distance of a Departing Aircraft

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xin He ◽  
Yaqing Chen ◽  
Yilong Ma ◽  
Dengfeng Hu ◽  
Haoran Gao
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Turbulence Model ◽  
Internal Flow ◽  
Aircraft Engine ◽  
Simulation Method ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Numerical Simulation Method

A hybrid numerical simulation method was established by combining the Spalart-Allmaras (SA) turbulence model and detached eddy simulation (DES). Numerical simulations were carried out to model cold and hot spray conditions of a nozzle without considering the internal flow of an engine to determine jet conditions. Analysis results show that the calculated hot spray results more in line with the reality. The jet effect of a typical aircraft engine was simulated numerically to determine the distance influenced by the jet blast from a departing aircraft engine.

Flow Visualization Experiments on Secondary Flow Patterns in an Isothermally Heated Curved Pipe

1987 ◽  
Vol 109 (1) ◽  
pp. 55-61 ◽  
Author(s):  
K. C. Cheng ◽  
F. P. Yuen
Keyword(s):  
Flow Visualization ◽  
Secondary Flow ◽  
Theoretical Models ◽  
Flow Patterns ◽  
Radius Of Curvature ◽  
Dean Number ◽  
Number Range ◽  
Curved Pipe ◽  
Curved Pipes ◽  
Numerical Predictions

Secondary flow patterns at the exit of a 180 deg bend (tube inside diameter d = 1.99 cm, radius of curvature Rc = 10.85 cm) are presented to illustrate the combined effects of centrifugal and buoyancy forces in hydrodynamically and thermally developing entrance region of an isothermally heated curved pipe with both parabolic and turbulent entrance velocity profiles. Three cases of upward, horizontal, and downward-curved pipe flows are studied for constant wall temperatures Tw=55–91°C, Dean number range K=22–1209 and ReRa=1.00×106–8.86×107. The flow visualization was realized by the smoke injection method. The secondary flow patterns shown are useful for future comparison with numerical predictions and confirming theoretical models. The results can be used to assess qualitatively the limit of the applicability of the existing correlation equations for laminar forced convection in isothermally heated curved pipes without buoyancy effects.

scholarly journals Research and Application of Filtering Grid Scale in Detached Eddy Simulation Model

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1252
Author(s):  
Liang Dong ◽  
Chao Guo ◽  
Ying Wang ◽  
Houlin Liu ◽  
Cui Dai
Keyword(s):  
Geometric Mean ◽  
Pressure Coefficient ◽  
Polar Angle ◽  
Internal Flow ◽  
Experimental Result ◽  
Detached Eddy Simulation ◽  
Quadratic Mean ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Pressure

The existing definition method of filter grid scale in a Detached Eddy Simulation (DES) hybrid model is unreasonable, which will lead to the unreasonable trigger of a boundary layer large eddy simulation and reduce computational efficiency. In view of this problem, the filter grid scale is discussed in this paper. The 90° square curved elbow is selected as the research object. The effects of three grid definition methods: geometric mean (ΔGM), arithmetic mean (ΔAM) and quadratic mean (ΔQM) on the simulation results of the DES model are compared, and the velocity distribution of the flow cross section and the distribution of the flow pressure coefficient on the outer arc surface are compared with the experimental results of Taylor. The results show that the order of the three definition methods is ΔGM≤ΔAM≤ΔQM. Meanwhile, within 30° < polar angle(θ) < 75°, the results are closer to the experiment, and the development trends and numerical values of ΔAM and ΔQM are closer to the experiment in general. However, when θ > 60°, the value of ΔQM is slightly closer to the experimental result than ΔAM. ΔQM is more suitable for calculating the internal flow in a curved elbow than the other two methods.

Effect of Curved Bar Properties on Bending of Curved Pipes

2000 ◽  
Vol 68 (4) ◽  
pp. 650-655 ◽  
Author(s):  
V. P. Cherniy
Keyword(s):  
Experimental Data ◽  
General Solution ◽  
Total Energy ◽  
Neutral Line ◽  
Radius Of Curvature ◽  
Thin Shells ◽  
Large Curvature ◽  
Curved Pipe ◽  
Curved Pipes ◽  
Thin Walled

A general solution is presented for in-plane bending of a thin-walled short-radius curved pipe. The problem is solved considering the properties of a curved bar—an actual radius of curvature of longitudinal fibers and the neutral line displacement. The theory is developed using minimization of the total energy. The relationships of the theory of elastic thin shells are used. The obtained results for the strains and stresses in curved short-radius pipe bends are compared with published theoretical and experimental data. The properties of a curved bar being taken into account enable to correct seriously the distribution and peak values of the strains which take place in curved pipes of large curvature subjected to bending.

Numerical simulation of rotating channel flow based on a modified DES model

2021 ◽  
pp. 2150193
Author(s):  
Peifeng Lin ◽  
Pu Wang ◽  
Yong Zhou ◽  
Xiaojun Li
Keyword(s):  
Channel Flow ◽  
Energy Transport ◽  
Turbulent Viscosity ◽  
Internal Flow ◽  
Additional Term ◽  
Detached Eddy Simulation ◽  
Turbulence Statistics ◽  
Eddy Simulation ◽  
New Type ◽  
Rotating Channel

A new type of nonlinear sub-grid scale (SGS) model is adopted based on the helicity analysis and is verified by predicting the internal flow in a rotating channel. A stress term that contains helicity constraint is introduced into the original SGS model to construct a nonlinear sub-grid model. This additional term representing the helicity constraint effect in the momentum equations is shown to give predictions that are in better agreement with the experimental data. In this paper, the Detached-Eddy Simulation (DES) and the nonlinear SGS model are used to further study the turbulence statistics of the rotating channel flow. Combining with the Reynolds stress transport equations and the turbulent kinetic energy transport equation, the change of turbulence statistics near the wall of the rotating channel is analyzed. The newly added term changes the turbulent viscosity near the wall, which changes the velocity gradient near the wall and further affects other turbulence statistics near the wall.

scholarly journals Assessment of Hybrid RANS/LES Models in Heat and Fluid Flows around Staggered Pin-Fin Arrays

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3752
Author(s):  
Byeong-Cheon Kim ◽  
Kyoungsik Chang
Keyword(s):  
Three Dimensional ◽  
Maximum Velocity ◽  
Fluid Flows ◽  
Channel Height ◽  
Detached Eddy Simulation ◽  
Mean Velocity ◽  
Pin Fin ◽  
Eddy Simulation ◽  
Pin Fin Arrays ◽  
Two Hybrid

In the present work, the three-dimensional heat and fluid flows around staggered pin-fin arrays are predicted using two hybrid RANS/LES models (an improved delayed detached eddy simulation (IDDES) model and a stress-blended eddy simulation (SBES) model), and one transitional unsteady Reynolds averaged Navier-Stokes (URANS) model, called k-ω SSTLM. The periodic segment geometry with a total of nine pins is considered with a channel height of 2D and a distance of 2.5D between each pin. The corresponding Reynolds number based on the pin diameter and the maximum velocity between pins is 10,000. The two hybrid RANS/LES results show the superior prediction of the mean velocity profiles around the pins, pressure distributions on the pin wall, and Nusselt number distributions. However, the transitional model, k-ω SSTLM, shows large discrepancies except in front of the pins where the flow is not fully developed. The vortical structures are well resolved by the two hybrid RANS/LES models. The SBES model is particularly adept at capturing the 3-D vortex structures after the pins. The effects of the blending function switching between RANS and LES mode of the two hybrid RANS/LES models are also investigated.

scholarly journals Research on Computational Method of Supersonic Inlet/Isolator Internal Flow

2021 ◽  
Vol 11 (19) ◽  
pp. 9272
Author(s):  
Zhuoran Liu ◽  
Caizheng Wang ◽  
Ke Zhang ◽  
Zhuo Zhao ◽  
Zhifeng Xie
Keyword(s):  
Shock Wave ◽  
Stokes Equations ◽  
Transport Model ◽  
Flow Simulation ◽  
Side Wall ◽  
Internal Flow ◽  
Computational Method ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Supersonic Inlet

In this research, a CFD solver is developed for solving the 2D/3D compressible flow problem: the finite volume method based on multi-block structural grids is used to solve the compressible Reynolds averaged Navier–Stokes equations (RANS). Included in the methodology are multiple high-order reconstruction schemes, such as the 3rd-order MUSCL (Monotone Upstreamcentered Schemes for Conservation Laws), 5th-order WENO (Weight Essentially Non-Oscillatory), and 5th-order MP (Monotonicity-Preserving) schemes. Of the variety of turbulence models that are embedded, this solver is mainly based on the shear stress transport model (SST), which is compatible with OpenMP/MPI parallel algorithms. This research uses the CFD solver to conduct steady-state flow simulation for a two-dimensional supersonic inlet/isolator, incorporating these high-precision reconstruction schemes to accurately capture the shock wave/expansion wave interaction and shock wave/turbulent boundary layer interaction (SWTBLI), among other effects. By comparing the 2D/3D computation results of the same inlet configuration, it is found that the 3D effects of the side wall cannot be ignored due to the existing strong lateral flow near the corner. To obtain a more refined turbulence simulation, the commercial software ANSYS Fluent 18.0 is used to carry out the detached eddy simulation (DES) and the large eddy simulation (LES) of the same supersonic inlet, so as to reveal the flow details near the separation area and boundary layers.

Study On the Applicability of URANS, LES and Hybrid LES/RANS Models for Prediction of Hydrodynamics of Cyclone Separator

2021 ◽  
Author(s):  
Sai Guruprasad Jakkala ◽  
S Vengadesan
Keyword(s):  
Fluid Flow ◽  
Flow Characteristics ◽  
Mesh Size ◽  
Turbulent Energy ◽  
Computational Time ◽  
Detached Eddy Simulation ◽  
Reynolds Stresses ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Rans Models

Abstract Cyclone separators are an integral part of many industrial processes. A good understanding of the flow features is paramount to efficiently use them. The turbulent fluid flow characteristics are modelled using URANS, LES and hybrid LES/RANS turbulent models. The hybrid LES/RANS approaches, namely DES (Detached Eddy Simulation), DDES (Delayed Detached Eddy Simulation) and IDDES (Improved Delayed Detached Eddy Simulation) based on the k - $\omega$ SST RANS approaches are explored. The study is carried out for three different inlet velocities (v = 8, 16:1, and 32 m=s). The results from hybrid LES/RANS models are shown to be in good agreement with the experimental data available in the literature. Reduction in computational time and mesh size are the two main benefits of using hybrid LES/RANS models over the traditional LES methods. The Reynolds stresses are observed in order to understand the redistribution of turbulent energy in the flow field. The velocity profiles and vorticity quantities are explored to obtain a better understanding of the behaviour of fluid flow in cyclone separators.

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