A Laboratory Study of the Effect of Surface Waves on Heat and Momentum Transfer at High Wind Speeds

Abstract

AbstractThis paper describes laboratory experiments (using a high‐speed wind‐wave flume) of the effects of water waves on heat and momentum exchange in the near‐water atmospheric boundary layer at high wind speeds. Different from previous experiments of this type, the parameters of waves were controlled by a net stretched along the entire channel to effectively decrease the fetch. This helped to achieve dependency of the transfer coefficients on two independent parameters, namely, the wind speed and fetch (expressed via variations of the wavefield). Another key to the experiment was using a stable temperature stratification of the air flow, with the temperature of the air entering the flume 15–25° higher than the water. The experiments showed a sharp increase in the heat exchange coefficient at winds exceeding 33–35 m/s, similar to that observed earlier in the high‐speed wind‐wave flume of Kyoto University with conditions of unstable temperature stratification of the air flow. The joint analysis of the data obtained in the high‐speed wind‐wave flumes of IAP RAS and Kyoto University yields the universal dependency of the exchange coefficients and the temperature roughness on the peak wave number of surface wave spectra. This is independent of the type of temperature stratification of the atmospheric boundary layer, either stable or unstable. The sharp increase in the heat exchange coefficient is shown to be associated with increased whitecapping.