The influence of buoyancy on pressure oscillation amplitude and frequency was studied with two steam jet directions in the range of steam mass flux 8.34–50.13 kg/(m²·s) and water temperature 40–85 °C. At small steam mass flux, the steam bubble pattern of vertical downward jet is attached bubble regime because the direction of steam momentum and buoyancy are opposite. The pressure oscillation frequency is less than 20 Hz, and the pressure oscillation amplitude is less than 1 kPa, which is much smaller than that for a vertical upward jet. It is conducive to the safety of relevant equipment. For the rough grown detached bubble regime, due to the influence of buoyancy, on the pressure oscillation frequency of vertical downward jet is smaller than that of vertical upward jet. Two dimensionless correlations of the pressure oscillation frequency were presented considering the influence of buoyancy. The prediction errors are within ±11%.

在蒸汽质量通量为 8.34-50.13 kg/(m ²·s) 和水温 40–85 °C。在小蒸汽质量通量下，由于蒸汽动量和浮力的方向相反，垂直向下射流的蒸汽气泡模式是附着气泡状态。压力振荡频率小于20 Hz，压力振荡幅度小于1 kPa，远小于垂直向上射流。有利于相关设备的安全。对于粗糙生长的分离气泡状态，由于浮力的影响，垂直向下射流的压力振荡频率小于垂直向上射流的压力振荡频率。考虑浮力的影响，提出了压力振荡频率的两个无量纲相关性。预测误差在±11%以内。