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.
In this application, AcuSolve is used to simulate the flow of water between concentric cylinders. The outer cylinder is held stationary while the
inner cylinder rotates with a constant speed. AcuSolve results are compared with analytical results as described in White (1991). The close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases containing thin annular gaps with flow induced by rotating walls.
In this application, AcuSolve is used to simulate the flow of mercury through a heated pipe. The AcuSolve results are compared with analytical results for pressure drop as described in White (1991), and with temperature
changes as described in Incropera and DeWitt (1981). The close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases with flow and imposed heat flux.
In this application, turbulent flow of air through a pipe is simulated. AcuSolve results are compared with experimental results as described in White (1991) and extracted from the Moody chart. The
close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model turbulent flow within pipes.
In this application, AcuSolve is used to simulate the viscous flow of water between a moving and a stationary plate with an imposed pressure
gradient. AcuSolve results are compared with analytical results described in White (1991). The close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases with imposed pressure gradients.
In this application, AcuSolve is used to simulate the flow of a highly viscous fluid between a moving and a stationary plate with an imposed
pressure gradient and fixed temperature on the walls. AcuSolve results are compared with analytical results described in White (1991). The close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases with imposed pressure gradients and viscous heating.
In this application, AcuSolve is used to simulate the flow of carbon dioxide (CO2) entering a pipe with a fixed velocity. AcuSolve results are compared with analytical results using the Hagen-Poiseuille approach as described in White (1991). The
close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases with constant flow velocity.
In this application, AcuSolve is used to simulate the transport of a passive scalar species in a fully developed laminar flow. AcuSolve results are compared with analytical results as described in Kays and Crawford (1993). The close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases with species transport.
In this application, AcuSolve is used to simulate the flow of air in an enclosed cylindrical cavity with a rotating top and a fixed bottom.
AcuSolve results are compared with experimental data adapted from Michelsen (1986). The close agreement of AcuSolve results with experimental data validates the ability of AcuSolve to model cases containing enclosed cavities with flow induced by rotating walls.
In this application, AcuSolve is used to simulate natural convection in the annular space between a heated inner pipe and an outer concentric pipe.
AcuSolve results are compared with experimental results adapted from Kuehn and Goldstein (1978). The close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model cases with flow induced by natural convection.
In this application, AcuSolve is used to simulate laminar flow through a channel with two outlets forming a T-junction. AcuSolve results are compared with experimental results adapted from Hayes and others (1989). The close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model cases with multiple outlet paths.
In this application, AcuSolve is used to simulate turbulent flow through a channel with a lower wall shaped as a sinusoidal wave. AcuSolve results are compared with experimental results adapted from Kuzan (1986). The close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model cases with internal flow through a channel with wavy walls.
In this application, AcuSolve is used to simulate high Peclet number laminar flow through a channel with heated walls. AcuSolve results are compared with analytical results adapted from Hua and Pillai (2010). The close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases involving heat transfer to a moving fluid with a high Peclet number.
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 the natural convection of a turbulent flow field within a tall rectangular cavity. AcuSolve results are compared with experimental results as described in Betts and Bokhari (2000). The close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model cases with natural convection of turbulent flow within a tall cavity.
In this application, AcuSolve is used to simulate fluid flow and viscous heating in an annulus formed by concentric cylinders. AcuSolve results are compared with analytical results adapted from Bird and others (1960). The close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases with viscous heating.
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 flow of mercury through a heated pipe. The AcuSolve results are compared with analytical results for pressure drop as described in White (1991), and with temperature
changes as described in Incropera and DeWitt (1981). The close agreement of AcuSolve results with analytical results validates the ability of AcuSolve to model cases with flow and imposed temperature constraints.
In this application, AcuSolve is used to simulate fully developed turbulent flow through an asymmetric diffuser with a divergent lower wall and
a straight upper wall. AcuSolve results are compared with experimental results as described in Buice and Eaton (1996). The close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model cases with internal turbulent flow with flow separation and reattachment in an asymmetric diffuser.
In this application, AcuSolve is used to simulate fully developed turbulent flow through an axisymmetric diffuser with a divergent upper wall and
a straight lower wall. AcuSolve results are compared with experimental results as described in Driver (1991) and on the NASA Langley Research Center
Turbulence Modeling Resource webpage. The close agreement of AcuSolve results with experimental data and reference turbulence model performance validates the ability of AcuSolve to model cases with turbulent flow with separation due to an adverse pressure gradient within an axisymmetric
geometry.
In this application, AcuSolve is used to simulate fully developed turbulent flow over a backward-facing step. AcuSolve results are compared with experimental results as described in Driver (1985) and on the NASA Langley Research
Center Turbulence Modeling Resource web page. The close agreement of AcuSolve results with experimental data and reference turbulence model performance validates the ability of AcuSolve to model cases with turbulent flow that forms a shear layer, recirculates and then reattaches downstream
of the divergent step.
In this application, AcuSolve is used to simulate fully developed turbulent flow through a channel containing a convex curve in the lower wall.
AcuSolve results are compared with experimental results as described in Smits (1979) and on the NASA Langley Research Center
Turbulence Modeling Resource webpage. The close agreement of AcuSolve results with experimental data and reference turbulence model performance validates the ability of AcuSolve to model cases with turbulent flow moving past a convex curved wall.
In this application, AcuSolve is used to simulate fully developed turbulent flow past a smooth hump on the lower wall of a flow domain. AcuSolve results are compared with experimental results as described in Seifert and Pack (2002) and on the NASA Langley Research
Center Turbulence Modeling Resource web page. The close agreement of AcuSolve results with experimental data and reference turbulence model performance validates the ability of AcuSolve to model cases with turbulent flow moving past a wall protrusion resulting in flow separation and recovery.
In this application, AcuSolve is used to simulate the heat transfer due to radiation between concentric cylinders. The inner and outer cylinders
are held at constant temperature and are defined to be radiation surfaces. AcuSolve results are compared with analytical results for temperature as described in Incropera (2006). The close agreement
of AcuSolve results with analytical results validates the ability of AcuSolve to model cases with radiation heat transfer requiring view factor computation.
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 turbulent flow through a strongly curved two dimensional 180 degree U-duct channel. AcuSolve results are compared with experimental results adapted from Rumsey et al. (2000). The close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model turbulent cases with strong curvature effects.
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 simulate the heat transfer due to conduction and radiation between concentric spheres. The inside surface
of the inner and the outside surface of the outer sphere are both held at constant temperature, while the gap between
them radiates the heat from one sphere to the other.
In this application, AcuSolve is used to simulate the heat transfer due to radiation through a specular interface within an absorbing, emitting,
but not scattering solid cube. One of the cube’s walls is modeled with an isotropic external radiation source while
the remainder of the cube is held at fixed temperature conditions and modeled with pure radiation, neglecting the
effects of conduction.
In this application, AcuSolve is used to simulate the wall heat flux due to nucleate boiling at a heated wall inside a rectangular channel with
water flow. Results are compared with experimental heat flux measurements as reported by Steiner, et al. (2005). The
close agreement of AcuSolve results with experimental results validates the ability of AcuSolve to model single phase nucleate boiling problems.
This section includes validation cases that consider unbounded simulation domains where external flow is present over
solid bodies, leading to free boundary layer development.
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.
In this application, AcuSolve is used to simulate fully developed turbulent flow past a smooth hump on the lower wall of a flow domain. AcuSolve results are compared with experimental results as described in Seifert and Pack (2002) and on the NASA Langley Research
Center Turbulence Modeling Resource web page. The close agreement of AcuSolve results with experimental data and reference turbulence model performance validates the ability of AcuSolve to model cases with turbulent flow moving past a wall protrusion resulting in flow separation and recovery.
In this application, AcuSolve is used to simulate fully
developed turbulent flow past a smooth hump on the lower wall of a flow domain. AcuSolve results are compared with experimental results as described
in Seifert and Pack (2002) and on the NASA Langley Research Center Turbulence Modeling
Resource web page. The close agreement of AcuSolve results with
experimental data and reference turbulence model performance validates the ability of
AcuSolve to model cases with turbulent flow moving past a
wall protrusion resulting in flow separation and recovery.
Problem Description
The problem consists of a fluid with material properties close to air flowing through a flow
domain containing a well-defined smooth hump with a slit opening at approximately 65
percent of the hump chord. The inlet of the domain is defined with an inflow
velocity in the streamwise direction that develops into fully turbulent flow at a
Reynolds number (Re) of 936,000, based on the hump chord length of 1.0 m. The
density of the flow medium is 1.0 kg/m3 and the dynamic viscosity is
1.0684 X 10-6 kg/m-s. The simulation is conducted with the Reynolds
Averaged Navier-Stokes equations using the Spalart Allmaras turbulence model, shear
stress transport (SST) model, the K-ω model and Realizable K-ε model to evaluate the
performance of the turbulence models. The flow predictions from AcuSolve are compared against experimental data and
previously published turbulence model performance for pressure and friction
coefficients within the domain.
The upper walls of the domain are specified as slip (inviscid) and the lower walls are specified
as no-slip. The inlet velocity and appropriate turbulence parameters are specified
in the streamwise direction to match the desired Reynolds Number of 936,000. The
outflow pressure is set to zero, and the lower wall on cavity below the hump is set
to slip. The problem is simulated as two dimensional with a single layer of elements
extruded in the cross stream direction and by defining the side walls as slip.
AcuSolve Results
The AcuSolve solution converged to a steady state and the results
reflect the mean flow conditions within the domain. The images below show contours
of velocity within the domain as well as the recirculation region directly
downstream of the hump. As the flow enters the domain with a bulk velocity, it
begins to develop a turbulent boundary layer near the lower wall prior to reaching
the hump. As the flow approaches the hump section, the velocity near the lower wall
decreases, but does not recirculate in front of the hump. It then accelerates over
the top of the hump and separates immediately after reaching the cavity opening. The
recirculation region propagates downstream, before the flow recovers and reattaches
to the lower wall.
The images below show the coefficient of pressure and coefficient of skin friction along the
lower wall of the flow domain plotted with experimental results. The non-dimensional
values are defined by the integrated inlet pressure and the magnitude of the inlet
velocity. The images show black circles representing the experimental measurements
(Seifert and Pack 2002), solid red lines for the SA model, solid blue lines for the
SST model, solid green lines for the K-ω model and solid cyan lines for the K-ε
model, representing the AcuSolve results. The resulting
pressure coefficient within the domain demonstrates that there are minor differences
between the three turbulence models. All three models are shown to perform
accurately in predicting the increase in surface pressure on the front of the hump,
but tend to over predict the skin friction in the wake of the hump, leading to an
over prediction of the reattachment location. The SA model predicts a slightly
larger recirculation region, and does not meet the expected recovery pressure
compared to SST, K- ω and K-ε. This performance was found to be consistent with
comparisons to other one equation models (NASA 2015).
Summary
In this application, a bulk turbulent flow at a Reynolds number of 936,000 within a flow domain
containing a wall-mounted hump is studied and compared against experimental data.
The AcuSolve results compare well with the experimental
data for pressure coefficient and skin friction coefficient near the hump and
downstream. The performance of the three turbulence models were found to be
consistent with previously published results for flow over a wall-mounted hump (NASA
2015). For this application, the two equation models appear to outperform the one
equation turbulence model, with better agreement for the downstream pressure on the
wall. This application demonstrates AcuSolve's ability
to predict the distribution of pressure and shear stress on protruding bodies within
a turbulent flow field and serves to validate current turbulence modeling
capabilities.
Simulation Settings for Turbulent Flow past a Wall-Mounted Hump
AcuConsole database file: <your working
directory>\wall_mounted_hump_turbulent\wall_mounted_hump_turbulent.acs
Global
Problem Description
Analysis type - Steady State
Turbulence equation - Spalart Allmaras
Auto Solution Strategy
Max time steps - 100
Convergence tolerance - 0.001
Relaxation factor - 0.4
Material Model
Fluid
Density - 1.0 kg/m3
Viscosity - 1.0684e-6 kg/m-sec
Model
Volumes
Fluid
Element Set
Material model - Fluid
Surfaces
+Y
Simple Boundary Condition
Type - Slip
-Y
Simple Boundary Condition
Type - Slip
Cavity walls
Simple Boundary Condition
Type - Wall
Turbulence wall type - Wall Function
Hump walls
Simple Boundary Condition
Type - Wall
Turbulence wall type - Wall Function
Hump walls - downstream
Simple Boundary Condition
Type - Wall
Turbulence wall type - Wall Function
Inlet
Simple Boundary Condition
Type - Inflow
Inflow type - Velocity
Inflow velocity type - Cartesian
X Velocity - 1.0 m/sec
Turbulence input type - Direct
Eddy viscosity - 3.205128e-6
m2/sec
Lower slip
Simple Boundary Condition
Type - Slip
Lower wall
Simple Boundary Condition
Type - Wall
Turbulence wall type - Wall Function
Nozzle walls
Simple Boundary Condition
Type - Wall
Turbulence wall type - Wall Function
Outlet
Simple Boundary Condition
Type - Outflow
Slip
Simple Boundary Condition
Type - Slip
References
A Seifert and L.G. Pack. "Active Flow Separation Control on Wall-Mounted Hump
at High Reynolds Numbers". AIAA Journal. 40(7). 2002.
NASA Langley Research Center Turbulence Modeling Resource web page.
http://turbmodels.larc.nasa.gov/nasahump_val.html. Accessed June
2015.