Tandem Cylinder Simulationsusing the Method of Your Choice

Some BodyAffiliated Somewhere

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Outline

• Objectives• Numerical Method• Flow Conditions• Grids• Results• Computational Resources• Observations

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Objectives

• State any objectives such as testing numerical method, turbulence model, grid convergence, etc

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Numerical Method

• Equations solved– Unsteady Reynolds-averaged Navier-Stokes (URANS) equations– Turbulence equations

• Spatial and temporal discretizations– Type of scheme (FD, FV, etc)– Design accuracy– Unique features of implementation

• Boundary Conditions

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Flow Conditions in Simulations

• Re = 166,000 based on D• Turbulence model run fully turbulent• Surface roughness strip placed at = 50 deg.

• M = 0.128

Grids

• Grid type (block-structured, unstructured, Cartesian)• # of Nodes or cells or …• Extent of grid (in plane and spanwise directions)

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Results:• Time step (in seconds)• Number of time steps run (total and for sampling)• Shedding frequency in Hz

• Time-averaged Drag (CD = fD/(D 0.5 |Vo|2) where fD is the force per unit span in the drag or streamwise direction, D = cylinder diameter) on front and rear cylinders

• Convergence information (e.g. history of Cprms after every 5000 time steps)

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Surface Pressure

Upstream Downstream

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RMS of Surface Pressure

Upstream Downstream

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Mean Velocity

• Along y/D=0

Gap Region Aft of Downstream

Cylinder

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Surface Pressure Spectra

Upstream, = 135o Downstream, = 45o

• Power Spectral Density

Computational Resources

• Computer hardware– CPU (type and number used)– Interconnect

• Resources– CPU (or wall clock) Time / time step

• # of time steps in simulation

– CPU (or wall clock) Time / 1 sec of simulation time• # of time steps needed for 1 sec of simulation time

– Memory used• Per cpu

• Total

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Observations

• What did you learn?– Computational challenges– New insights into the physics– Assessment of state-of-the-art based on your simulation

for the problem category of interest– Benchmark deficiencies– Recommendations for follow-on efforts

• Additional measurements

• Desired additions/modifications to problem statement

• Procedures for computations or measurements

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OPTIONAL

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Surface Pressure Correlation

• Spanwise row of sensors at =135 deg

Upstream Downstream

z

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Surface Pressure Coherence

• Spanwise row of sensors at =135 deg• Coherence at shedding frequency = 178 Hz

Upstream Downstream

z

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2D TKE

• 1/2 (u' u' + v' v' + w' w')/)/Vo2

Gap Region Aft of Downstream

Cylinder

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2D TKE• 1/2 (u' u' + v' v' + w' w')/)/Vo

2 along y/D=0

Gap Region Aft of Downstream

Cylinder

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2D TKE

Gap Region, x/D=1.5 Aft of Downstream

Cylinder, x/D=4.45

• 1/2 (u' u' + v' v' + w' w')/)/Vo2

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Acoustic Radiation

Spectra

• Significant peaks at harmonics