The known similarity between the wavy weld interface observed in high‐velocity impact welding of metals and the wakes behind an obstacle in a uniform stream was analyzed. The wavelength, the wave size, and the wave shape were established in terms of semi‐empirical relationships. The energy consumed in the formation of the interface wave was found to be over 90% of the collision energy for copper to steel welds. The Mathieu function was found to provide a very good approximation to the wave shape. The analysis was based on applying Birkhoff’s model of the swinging Foppl wake behind an obstacle as an analogy to determine the shape and size of the developed waves.