Obtaining velocity and pressure distributions in natural convection flows using experimental temperature fields

Abstract

New hybrid simulation technique is proposed for natural convection flows, which combines experimental measurements of the instantaneous temperature fields with numerical integration of the fluid dynamics equations. Experimental temperature distributions are used to determine the buoyancy term, which enables one to obtain the velocity and pressure fields without extra measurements. Solution of the energy equation is replaced with experimental data, hence the technique can be used even if the energy equation contains unknown source terms or if the boundary conditions for temperature are unknown. The approach is demonstrated for Background Oriented Schlieren (BOS) measurements of three natural convection flows: natural convection near a heated vertical plate, convective plume from a heated horizontal wire and horizontal convection driven by nonuniform radiative heating of liquid surface. The velocity fields, obtained by reconstruction in steady and unsteady flows, exhibit good agreement with numerical simulations if the input temperature data are accurate. Moreover, the hybrid simulation takes into account the flow asymmetries in a particular experimental run. However, spatially limited measurement region or underestimation of the peak temperature, typical for BOS measurements of the thin thermal layers in liquids, lead to underprediction of the velocity and pressure disturbances in hybrid simulation. • Velocity and pressure fields are determined from the measured temperature fields. • The proposed approach is validated for three different natural convection flows. • Instantaneous temperature fields are measured using Background Oriented Schlieren. • The proposed approach can be used if the problem contains unknown heat sources. • Influence of temperature uncertainty and limited measurement region is analyzed.