Experimental and numerical study on the circumferential pressure distribution on the wall of a 90° elbow pipe with circular section

The 90° elbow is used as the pressure difference sensor to measure the helium mass flow rate in HTR-PM. Water experiments and numerical simulation with a 1/3 scaled model are conducted to study the pressure distribution on the wall of the elbow. Pressure information around the elbow with the inner diameter of 80 mm and the ratio of bending radius to diameter of 1.5 is measured by utilizing compactly arranged pressure tappings on the wall of the elbow, and compared with numerical results obtained by using the RNG k-ε model. The influence of pressure tapping hole on the measuring results is analyzed to evaluate the origin of the measurement error. The results reveal that the shape of the circumferential pressure distribution curve is similar to a sine wave and the FFT method is applied to analyze the phase-frequency characteristics. Reconstruction equation is put forward to describe the circumferential pressure distribution with the FFT results. The value of the frequency fi and phase φi of the ith sinusoidal component is determined by the flow symmetry, and equations are proposed to calculate the theoretical values.