This dataset contains the instantaneous velocity vector fields as well as the time averaged velocity and turbulence fields from PIV data taken over a large acrylic plate fouled with a relatively uniform diatomaceous biofilm. See associated article, Roughness effects of diatomaceous slime fouling on turbulent boundary layer hydrodynamics, for methods description. Time averaged velocity and turbulence fields data are stored in the file velocity_fields.mat, which contains the following variables: X: The streamwise distance of each column in the velocity field matrices [mm] Y: The vertical distance (from the bottom of the frame) of each row in the velocity field matrices [mm] U: Time averaged streamwise velocity [m s^-1] V: Time averaged vertical velocity [m s^-1] tke: Time averaged turbulent kinetic energy [m^2 s^-2] u': Time averaged streamwise Reynolds stress [m^2 s^-2] v': Time averaged vertical Reynolds stress [m^2 s^-2] u'v': Time averaged Reynolds shear stress [m^2 s^-2] The zip file biofilm_vector_fields contains the 4,000 statistically independent velocity vector fields used to compute the time averaged velocity and turbulence fields. The vector field data is in the variable labeled matr. Size calibration: 2302 pixels/ inch (906.3 pixels/ cm). Column 1: X (streamwise distance in [pixels]) Column 2: Y (wall-normal distance from bottom of frame in [pixels]) Column 3: U (streamwise velocity vector in [pixels / 250 microseconds]) Column 4: V (vertical velocity vector in [pixels / 250 microseconds]) Column 5: CHC (number of tracked particles. A value < 1 gives the location of the biofilm, which was masked out) Column 6: U2 Column 7: V2 Column 8: U3 Column 9: V3 Column 10: U4 Column 11: V4