HPC is a classifying system invented for this project. The purpose of it was to classify each of the 6 holes made for this project, and after the experimentation was complete, conclude the results based on the HPC number of each hole. There could be an endless amount of different holes, so the classification system gave any hole its own classification number. It also meant that from the holes experimented on; different properties for the effects a certain hole in an airfoil would have on surrounding airflow, could be discovered. The Hole Properties Coefficient consists of 6 coefficients, each telling information about the proportions and co-ordinates of the hole in relation to the airfoil. It’s relatively simple to calculate the HPC of a hole in an airfoil. Below are the formulas needed to find the HPC of a hole.
In case only the HPC of a hole is know, several identities about the hole could be found just by looking at the HPC of the hole. Below are some equations which will enable one to visualize the shape and dimensions of the hole.
Example of Calculating HPC of a hole
Given S = 240 mm Au = 48 mm Al = 52mm Eu = 63 mm
C = 160 mm Bu = 78 mm Bl = 80mm El = 62 mm
Calculations
K 1u = Bu/S x 100 = 33
K 2u = Au/C x 100 = 30
K 3u = Eu/C x 100 = 39
K 1l = Bl/S x 100 = 33
K 2l = Al/C x 100 = 21
K 3l = El/C x 100 = 38
Therefore HPC 33 30 39 – 33 32 38
K 1 = K 1u / K 1l
K 1 = 1 Therefore the Length the upper hole is the same as the Length of the lower hole.
K 2 = K 2u / K 2l
K 2 = 0.9 Therefore the Width of the upper hole is smaller then the Width of the lower hole.
K 3 = K 3u / K 3l
K 3 = 1 Therefore the direction of the hole is perpendicular to the chord of the airfoil.