Hello, I’m designing a 2D wind tunnel model for my master thesis. It will be a profile equipped with a fixed hinged trailing edge flap. I’m going to measure at different angle of attacks and different flap settings at low speeds (about 70 to 100 m/s). The aim is to measure steady and unsteady pressure distributions. To calculate the maximum scale of the model I have to consider the maximum blockage ratio of 5% - 10% (which I found in the public literature). My question is no which area of the model do I have to set in relation of the wind tunnel cross section area? Is it the in x-axis projected frontal area of the model (considering the angle of attack and the flap deflection) or is it the maximum thickness of the airfoil times model span? The wind tunnel will has a closed test section and doesn’t have slotted walls. I’m looking forward to your comments!