抄録
Investigations of time-dependent laminar and transitional flows need accurate and reproducible generation of the flow as a function of time. For this purpose, an electronically controlled air valve, with which the mass flow rate is controlled, was designed and built. The working principle and lay-out of the valve are explained and the performance of the valve is demonstrated. It was found that with the present equipment one can study any nonperiodic and periodic flow and the flow can be adjusted to be laminar, transitional and turbulent. The investigations on laminar and transitional time-dependent flows are reported. Laminar flow investigations showed that the generated sinusoidal mass flow rates agree well with that of analytical solution. Non-periodic transient and periodic sinusoidal pulsatile transitional flows were investigated. It was shown that elucidation of the transition in non-periodic transient flows may help in understanding the transition in periodic flows.
