Introduction of background knowledge regarding flow physics and CFD as well as detailed information about the use of AcuSolve and what specific options do.
Collection of AcuSolve simulation cases for which results are compared against analytical or experimental results to demonstrate the accuracy
of AcuSolve results.
This section includes validation cases that consider unbounded simulation domains where external flow is present over
solid bodies, leading to free boundary layer development.
In this application, AcuSolve is used to simulate turbulent flow of air through and behind a two dimensional open-slit V. AcuSolve results are compared with experimental results adapted from Yang and Tsai (1993). The close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model the Coandă effect.
In this application, AcuSolve is used to simulate turbulent flow of a fluid over a NACA 0012 airfoil at 3 angles of attack, 0 degrees, 10
degrees, and 15 degrees. AcuSolve results are compared with experimental results for coefficients of pressure, lift, and drag reported by NASA. The
close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model external aerodynamics.
In this application, AcuSolve is used to simulate two dimensional, laminar flow over a cylinder to predict separation of flow from the cylinder
surface and the flow in the wake area. AcuSolve results are compared with experimental results as described in Tritton (1959). The close agreement of
AcuSolve results with experimental results validates the ability of AcuSolve to model cases with unsteady oscillating vortex streets.
In this application, AcuSolve is used to simulate the separation of laminar flow over a blunt plate. AcuSolve results are compared with experimental results as described in J.C. Lane and R.I. Loehrke (1980). The close
agreement of AcuSolve results with the experimental results validates the ability of AcuSolve to model cases with external laminar flow including separation.
In this application, AcuSolve is used to simulate the mixing of two streams of fluid with different velocities moving past a splitter plate.
AcuSolve results are compared with experimental results as described in J. Delville, et al. (1989). The close agreement of
AcuSolve results with the experimental results validates the ability of AcuSolve to model mixing layers in the turbulent flow regime.
In this application, AcuSolve is used to solve for the flow field around a high lift airfoil with inflow conditions that lead to transitional flow
on the pressure and suction side of the airfoil's surface. The moderate level of turbulence intensity at the inlet,
low angle of attack and shape of the airfoil induce a transition to turbulent flow after a separation bubble develops
on the surface. The coefficient of pressure is compared against experimental data from laboratory experiments.
In this application, AcuSolve is used to simulate the fluid-structure interaction of a fluid moving over a cylinder/plate assembly. AcuSolve results are compared with experimental results as described in Gomes and Lienhart (2009). The close agreement of
AcuSolve results with the experimental results validates the ability of AcuSolve to model cases in which the fluid forces lead to structural motions.
In this application, AcuSolve is used to solve for the flow and temperature field within a channel containing a heated wall. The wall is maintained
at a constant temperature, inducing heat flux into the fluid, to predict the thermal law of the wall. The non-dimensional
temperature versus the non-dimensional height above the wall is compared to the analytical correlation provided by
Kader.
This section includes validation cases containing conditions producing laminar to turbulent flow that are simulated
with a turbulence transition model.
This section includes validation cases that consider time dependent motion within the domain, requiring that the mesh
movement be modeled with a differential equation, a fully defined mesh motion or by interpolated mesh motion.
Collection of AcuSolve simulation cases for which results are compared against analytical or experimental results to demonstrate the accuracy
of AcuSolve results.
This section includes validation cases that consider unbounded simulation domains where external flow is present over
solid bodies, leading to free boundary layer development.
In this application, AcuSolve is used to solve for the flow and temperature field within a channel containing a heated wall. The wall is maintained
at a constant temperature, inducing heat flux into the fluid, to predict the thermal law of the wall. The non-dimensional
temperature versus the non-dimensional height above the wall is compared to the analytical correlation provided by
Kader.
In this application, AcuSolve is used to solve for the
flow and temperature field within a channel containing a heated wall. The wall is maintained
at a constant temperature, inducing heat flux into the fluid, to predict the thermal law of
the wall. The non-dimensional temperature versus the non-dimensional height above the wall
is compared to the analytical correlation provided by Kader.
Problem Description
The problem consists of a fluid having material properties close to air with a density of 1.0
kg/m3, molecular viscosity of 0.0001 kg/m-s, specific heat of 1005.0
J/kg-K and thermal conductivity of 0.139 W/m-K. The properties are specified to
obtain a Prandtl number of 0.72. The velocity is defined as periodic and is driven
by a constant acceleration body force equal to 2.0 m/s2. The temperature
is specified as periodic+unknown ratio allowing it to develop until it reaches a
steady solution. The simulation description is shown in the following image, which
is not drawn to scale. The model is simulated using the one equation Spalart
Allmaras turbulence model along with the advective-diffusive temperature equation.
The thermal wall distribution is validated against correlation data published by
Kader 1981.
The simulation was performed as a two-dimensional problem by constructing a volume mesh that
contains a single layer of elements extruded in the cross-stream direction, normal
to the flow plane and by imposing periodic boundary conditions on the extruded
planes. The streamwise direction contains two elements allowing the flow and
temperature solution to develop. Only the lower half of the channel is modeled,
assuming the solution is mirror across the top slip plane.
AcuSolve Results
The AcuSolve solution converged to a steady state and the results
reflect the mean flow conditions within the channel. The simulation results
demonstrate that the channel wall induces a thermal flux into the flow field,
producing a temperature distribution dependent on the distance from the wall. The
thermal law of the wall computed from the AcuSolve
results is compared with correlation data for the corresponding Prandtl number, as
demonstrated in Kader 1981. The plot shown below gives the non-dimensional value of
T+ as a function of Y+, where T+ and Y+ are computed per the following
relationships:(1)
(2)
(3)
Where , is the fixed wall temperature,
T is the temperature away from the wall,
is the fluid density, is the fluid specific heat, is computed from the magnitude of the shear stress
and is the local surface heat flux.
The image below shows black circles representing the correlation data and a solid red line for
the AcuSolve results. The results demonstrate that the
temperature distribution away from the wall is resolved properly and compares well
with the correlation. Since an empirical relationship for T+ is used for comparison,
there will be minor discrepancies compared with the simulation results. Additional
comparisons have been made against DNS results for T+ from Kawamura et al. 1998.
Summary
The
AcuSolve solution compares well with the correlation data for turbulent flow within a heated channel. In this application, the constant temperature wall induces a surface heat flux, giving rise to a temperature gradient within the channel.
AcuSolve can capture the correct temperature gradient at any location above the wall if an appropriate first layer height is selected to resolve a Y+ value of 1.0. The good agreement with correlation data for T+ demonstrates that
AcuSolve can predict the locally varying temperature distribution within a turbulent channel.
Simulation Settings for Turbulent Flow Through a Heated Periodic Channel
SimLab database file: <your working
directory>\channel_periodic_heat\channel_periodic_heat.slb
Global
Problem Description
Flow type - Steady State
Temperature equation - Advective Diffusive
Turbulence equation - Spalart Allmaras
Auto Solution Strategy
Max time steps - 50
Convergence tolerance - 0.0001
Relaxation Factor - 0.4
Temperature - On
Material Model
Fluid
Type - Constant
Density - 1.0 kg/m3
Viscosity - 1.0e-4 kg/m*sec
Specific Heat - 1005.0 J/kg*K
Conductivity - 0.139 W/m*K
Body Force
BodyForce
Gravity
X-component - 2.0 m/sec2
Model
Volumes
Fluid
Element Set
Material model - Fluid
Body force - BodyForce
Surfaces
Symmetry_1
Simple Boundary Condition - (disabled to allow for periodic
conditions to be set)
Symmetry_2
Simple Boundary Condition - (disabled to allow for periodic
conditions to be set)
Inflow
Simple Boundary Condition - (combination of integrated BC and
periodic BC set)
Advanced Options
Integrated Boundary Conditions - Temperature -
300.0 K
Outflow
Simple Boundary Condition - (disabled to allow for periodic
conditions to be set)
Slip_surface
Simple Boundary Condition
Type- Slip
Wall_surface
Simple Boundary Condition
Type- Wall
Temperature BC type - Value
Temperature - 350.0 K
Periodics
2D
Periodic Boundary Conditions
Type - Periodic
Flow
Periodic Boundary Conditions
Type - Periodic
Temperature
Individual Periodic BCs
Temperature: Type - Single Unknown Ratio
Nodes
Zero_z-velocity
Z-Velocity: Type - Zero
References
B.A. Kader, "Temperature and concentration profiles in fully turbulent boundary
layers", International Journal of Heat and Mass Transfer, Volume 24, Issue 9,
1981, Pages 1541-1544.
H. Kawamura, K. Ohsaka, H. Abe and K. Yamamoto, "DNS of turbulent heat transfer
in channel flow with low to medium-high Prandtl number fluid", International
Journal of Heat and Mass Transfer, 19:482-491, 1998.