Experimental investigation of pressure statistics in laboratory homogeneous isotropic turbulence

Pressure gradient and pressure play a key role in the evolution of structures and energy redistribution in turbulence. However, experimental investigations of pressure statistics in turbulent flows are difficult. With development in optical Lagrangian particle tracking (LPT) techniques over the past decades, it is now possible to obtain the pressure gradient fields with high accuracy from the measured acceleration fields, which gives an inspiration to study pressure statistics experimentally. In this work, we construct the instantaneous pressure and pressure gradient fields by the divergence curl correction method, using Lagrangian particle tracking data from laboratory turbulence generated in our turbulence exploration apparatus (TEA), which is newly developed with eight forcing elements arranged symmetrically in space. The measured velocity and acceleration statistics show that the laboratory turbulence in the TEA system is very close to be homogeneous and isotropic. The statistics of pressure gradient and velocity correlation conditioned on velocity confirm the interesting role of pressure gradient in the redistribution of energy in turbulence. In particular, these statistics of pressure gradient are not sensitive to spatial filtering with a filter size up to the lower end of the inertial range, indicating that these statistics capture the characteristics of the pressure gradient at scales in the inertial range or above.