Drag Force Measurement 1 ME 322 THERMOFLUIDS LAB1

Drag Force Measurement 1 ME 322 THERMO-FLUIDS LAB-1 1/10/2022

Drag Force Measurement 2 � In many situations we are interested in calculating the drag force acting on objects (ex. Airfoils, airplanes cars, buildings etc. ) � One way is to solve the flow governing equations, Navier. Stokes equations (computationally intensive, time consuming, turbulence modeling) � Alternatively, we can measure the drag force in a wind tunnel � Drag force measurement can be done in two ways: Force Balance Wake Survey ME 322 THERMO-FLUIDS LAB-1 1/10/2022

Drag Force Measurement 3 � Force Balance The model is mounted on a sting (holder) inside the wind tunnel Force Balance can be internal (inside the model) or external (outside the wind tunnel) Balances can measure 1, 2, 3 -6 components (3 forces and 3 moments) ME 322 THERMO-FLUIDS LAB-1 1/10/2022

Drag Force Measurement 4 � Force Balance ME 322 THERMO-FLUIDS LAB-1 1/10/2022

Drag Force Measurement 5 � Wake Survey In this method a momentum balance is used to estimate the drag force Using a control volume enclosing the model, if the velocity and pressure are known along the control volume surface we can apply the momentum equation to the control volume. The drag force will be an external force applied on this control volume CS y x CS CV ME 322 THERMO-FLUIDS LAB-1 1/10/2022

Drag Force Measurement 6 � CS y x CS CV ME 322 THERMO-FLUIDS LAB-1 1/10/2022

Drag Force Measurement 7 � CS y 4 1 x 3 CV 2 ME 322 THERMO-FLUIDS LAB-1 1/10/2022

Drag Force Measurement 8 � ME 322 THERMO-FLUIDS LAB-1 1/10/2022

Drag Force Measurement 9 � http: //www. unitedsensorcorp. com/rakes. html ME 322 THERMO-FLUIDS LAB-1 1/10/2022