Computation of an Unsteady Orifice Flow in a Circular Pipe From Wall Pressure Measurements Based on Measurement-Integrated Simulation Using a Turbulent Model

Visualizing the state of real turbulent flow is important in many applications such as safe operation and fault diagnosis in plant or pipeline. Two approaches to this purpose exist: experimental measurement and numerical simulation. In experimental measurement, reliability of the result at measured point is easy to evaluate. However, information of the whole flow field is difficult to obtain. On the other hand, numerical simulation easily obtains any information of the flow field. However, the reliability of the result strongly depends on the numerical model and boundary condition and/or the initial condition. In general, the more precise results are needed, the heavier computation load we spend. None of these approaches is superior, and combination methods of them are subjected to extensive research. Above all, we particularly paid attention to measurement-integrated (MI) simulation proposed by Hayase et al. MI simulation can expect to reduce computational load. We have applied MI simulation to unsteady oscillatory airflows passing through an orifice. In our previous study, a standard k-ε model was used for MI simulation. Estimation error remained due to inadequate consideration of the feedback law. In our latest study, the feedback law was decided considering an effect of computation grid on CFD of contracted flow. As a result, wall pressures near the orifice plate and axial velocities on vena contracta estimated with MI simulation showed good agreement with that of measurement. In the present paper, we deal with visualization of unsteady oscillatory airflows passing through an orifice from wall pressure measurement based on MI simulation using a turbulent model. The former studies have used measured inlet flow rate which is unknown in many actual case. Compared with the flow rate measurement, wall pressure measurement is simple. Therefore, we consider MI simulation using only wall pressure are of practical use. The developed MI simulation was performed with unsteady flow rate with the frequency up to 10 Hz. Computation results obtained with the developed MI simulation using coarse computation grid is compared with experimental results. It is confirmed that flow field obtained with the developed MI simulation is close to that of experiment.