The Choice of Turbulence Models for Steam Jets

Abstract

The noise from the steam dumping is a serious problem for many industries. For example, the popping of pressure relief valves of power boilers causes a temporal sound level overshoot over the admissible one up to 30-40 dBA in a radius of several kilometers. Mathematical modeling is an important tool for studying the outflow steam jets. Knowing processes of steam efflux into the atmosphere allows us correctly to calculate noise levels at a distance from them on the one hand and on the other hand to realize measures for sound attenuation. The study of mechanisms of noise generation by jets had begun in the end of 1940s and had been generally related to investigations of air jets and exhaust gas jets of aircrafts. The choice of turbulence models for steam jets has been studied insufficiently until recently. The significant subject of the steam jet simulation is the choice of the turbulence model. There are about a dozen mathematical models of turbulence, which are implemented in different software packages. In the case of simulation of turbulent flows with transient large scale vortex structures, it is ineffective and impossible to solve Reynolds averaged Navier-Stokes equations closed using semi empirical turbulence model or by means of the direct numerical simulation (DNS). Simulation of three dimensional and nonstationary vortices is carried out using a Large Eddy Simulation (LES) method in which the idea of the formal mathematical differentiation of coarse and fine structures by means of either operation, for example the filtration operation, is recommended. It is noted that, based on the LES method, it is possible to compute the coherent vortex structures, and the applicability of the model for prediction of noise generated by steam jets. LES model describes noise generation processes from steam jet more correct.