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fluent噪音模拟例子

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  • 开发语言:Others
  • 实例大小:0.98M
  • 下载次数:9
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  • 发布时间:2020-07-08
  • 实例类别:一般编程问题
  • 发 布 人:robot666
  • 文件格式:.pdf
  • 所需积分:2
 

实例介绍

【实例简介】
为运用fluent进行噪音模拟的同学们提供帮助
Modeling Flow-Induced (Aeroacoustic) Noise Problems Using FLUENT Step 1: Grid 1. Read the grid file cylinderedmsh Fle→Read→Case As Fluent read s the grid file, it will report its progress in the con sole wi n.doi Since the grid for this tutorial was created in meters, there is no need to rescale the grid. Check that the domain extends in the x-direction from -0.095 m to 0.38 m.e 2. Check the grid Grid→ Check FLUENT will perform various checks on the mesh and will report the progress in the console window. Pay particular attention to the reported minimum volume. Make sure this is a positive number 3. Reorder the grid Grid→ Reorder→ Domain To speed up the solution procedure, the mesh should be reordered, which will substan- tially reduce the bandwidth and make the code run faster UENT will report its progress in the console window > Reordering domain using Reverse Cuthill-McKee method: zones. cells, faces. done Bandwidth reduction = 32634/253= 128.99 Done Fluent Inc. May 11. 2005 3 Modeling Flow-Induced (Aeroacoustic) Noise Problems Using FLUENT 4. Display the grid pay→Grid. Grid Display Options Edge Type Sur facet H odes A default-interior inlet I Edges w Feature outlet symmetry bottom symmetry【op a Partitions wall cylinder Shrink facto Surtace t驴e彐 Surface name patttel dip-sur Match thus -fE Oulline Iuleriur Display Colo Close Help (a) Display the grid with the default settings(Figure 2) Use he niddle nouse buller lo zoon in or Che image so you can see che Inesh near the cylinder(Figure 3) Fi 2: Grid Displa Modeling Flow-Induced (Aeroacoustic) Noise Problems Using FLUENT Figure 3: The Grid Around the Cvlinder Quadrilateral cells are used for this LES simulation because they generate less numerical diffusion than triangular cells. The cell size should be small enough to capture the relevant turbulence length scales, and to make the numerical diffusion smaller than the subgrid-scale turbulence viscosity The mesh for this tutorial has been kept coarse in order to speed up the calculations. A high guality les simulation will require a finer mesh near the cylinder wall Fluent Inc. May 11. 2005 Modeling Flow-Induced (Aeroacoustic) Noise Problems Using FLUENT ep 2: Models 1. Select the segregated solver with second-order implicit unsteady formulation D f efine ModelsS Sover Spuer Formulation 令Sequ Implicit v Coupled Spa Time Axisymmetric Unsteady v AXisymmetric swirl Transient control H Non-lteratiue Time Advancement velocity Fomulation Unsteady Formulation Absolute y nclativc y lat ordcr Implicit 令2md- order Implicit Grad ient option Porous formulatio Cell-Based A Superficial velocity o Node-Based Physical velocit OK Cancel Help (a) retain the default selection of Segregated under Solver Under Time, select Unsteady (c Under Transient Controls, select Non-Iterative Time Advancement ( d) Under Unsteady Formulation, select 2nd-Order Implicit Under Gradient Option, select Node-Based (f)Click OK 6 Modeling Flow-Induced (Aeroacoustic) Noise Problems Using FLUENT 2. Select the les turbulence model The LEs turbulence model is not available by default for 2D calculations. You can make it available in the gui by typing the following command in the fluent console window (rpsetvar 'les-2d? #t) Define→ Models→ Viscous Viscous odel yodel Model constants Inviscid Cs Laminar 5 paart- lleras〔 I eqn〕 k-epsilon (2 eqn] yk (2 qnp v Reynolds stress (5 eqi r Detached eddy simulation Large Eddy Simulati Subgnid-Scale Model Smagorinsky-Lilly User-Defined functions PALE Subgrid-Scale Turbulent viscosity y kinetic-Energy Transport TiTH Options a Dynamic Model oK Cancel Help (a) Under Model, select Large Eddy Simulation (b)retain the default option of Smagorinsky-Lilly under Subgrid-Scale Model (c) Retain the default value of 0. 1 for the model constant Cs (d) Click OK You will see a warning dialog bo. c, stating that Bounded Central-Differencing default for momentum with LES/DES. Click OK The LES turbulence model is recommended for aeroacoustic simulations because LeS resolves all eddies with scales larger than the grid scale. Therefore, wide band aeroa- coustic noise can be predicted using LES simulations Fluent Inc. May 11. 2005 Modeling Flow-Induced (Aeroacoustic) Noise Problems Using FLUENT ep 3 Materials You will use the default material, air, which is the working luid in this proble. The default properties will be used for this simulation Define→ Materials Retain the default valuc of 1.225 for Retain the default value of 1.7894e-05 for Viscosity needed. For details, refer the chapter Physical Poperties in the FLUENT User's Guide e if You can modify the fluid properties for air or copy another material from th e database if Step 4: Operating Conditions Define-Operating Conditions 1. Retain the default value of 101325 Pa for the Operating pressure Step 5: Boundary Conditions 1. Retain the default conditions for the fluid Define> Boundary Conditions (a) Undcr Zone, sclect fluid The Type will be reported as fluid (b) Click Set... to open the Fluid par i. Relain the default selection of air as the luid naterial in the Material Name drop-down list ii. Click OK 2. Set the boundary conditions at the inlet (a) Under Zone, select inlet The Type will be reported as velocity-inlet (b) Click Set. to open the Velocity Inlet panel i. Set the Velocity Magnitude to 69. 2 m/s ii. Retain the default No Perturbations in the Fluctuating velocity algorithm drop-down list, and click OK This tutorial does not make use of fluent's ability to impose inlet pertur- balions al velocily inlets wleT using LES. Il is assumed chal all unsteadiness is due to the presence of the cylinder in the flou Modeling Flow-Induced (Aeroacoustic) Noise Problems Using FLUENT 3. Set the boundary conditions at the outlet (a under Zone, select outlet The Type will be reported as pressure-outlet (b)Click Set... to open the Pressure Outlet panel i. Confirm that the Gauge Pressure is set to o ii. Retain the default option of Normal to boundary in the Backflow Direction Specification Method drop-down list, and click OK The top and bottom, boundaries are set to sgmmetry boundaries. No user input is required for this boundary tyr Step 6: Quasi-Stationary Flow Field solution Before extracting the source data for the acoustic analysis, a quasi-stationary How needs to be established. The quasi-stationary state will be judged by monitoring the lift and drag forces 1. Set the solution controls Solve-Controls→ Solution Solution controls Equations E Non-Iterative Solver Controls Flow Hax Correction residual relaxation Corrections Tolerance Tolerance Factor Pressure 1 Pressure-velocity coupling PSO Discretization Neighbor Correction Pressure PRESTO! 1 Momentum Bounded Central Differen Y OK Default Cantel Help (a) Retain the default PISO scheme for Pressure-Velocity Coupling ( b) Undcr Discretization, select PRESTO! in the Pressure drop-down list PRESTO! is a nore accurale scherne /or interpolating Jace pressure values Tom Fluent Inc. May 11. 2005 Modeling Flow-Induced (Aeroacoustic) Noise Problems Using FLUENT (c) Retain the defaull Bounded Central Differencing for Momentum For LES calculations on unstructured meshes, the Bounded Central Differencing scheme is recommended for Momentum (d) Set the Relaxation Factor for Pressure to0.75 (e) Relain the default Relaxation Factor for The pressure field is relaced only during the initial transient phase. The relax ation Factor for Pressure will be increased to 1 at a later stage (f)Click OK 2. Initialize the solution Solve-Initialize-Initialize (a) Initialize the flow from the inlet conditions by selecting inlet in the Compute From drop-down list b)Click Init to initialize the solution and click Close 3. Enable the plotting of residuals Solve- Monitors>Residual (a)Select Plot under Options (b) Under Storage, enter 10000 Iterations (c) Under Plotting, enter 20 Iterations (d) Retain the default values for the othcr paramctcrs and click OK 4. Set thle time step paraneters Solve -Iterate (a) Set the Time Step Size(s)to 5e-6 The time step size required in LES calculations is governed by the time scale of the smallest resolved eddies. That requires the local Courant-Friedrichs-Leuy (CFL) number to be of an order of 1. It is generally difficult to know the proper time step sixe at the beginning of a simulation. Therefore, an adjustment after the flow is established, is often necessary. For a given time step At, the highest frequency that the acoustic analysis can produce is fon. For the time step siz selected here, the macimum frequency is 100kH2. typically in most aeroacoustic calcalation.s, the maximum frequency obtained from the analy si s is higher than the audible range of interest 10 O Fluent Inc. May 11, 2005 【实例截图】
【核心代码】

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