EFFECT OF DISPERSED PHASE ON MODIFICATION OF TURBULENT-FLOW IN A WALL-JET

The interaction between dispersed particles and fluid turbulence for a vertical downflow turbulent wall jet embedded in a uniform stream was investigated experimentally and numerically Three kinds of size class ified spherical particles, which were smaller than the Kolmogorov leng thscale of the flow were dispersed in the jet upstream of the test sec tion. The particle mass loading ratios were set at up to 0.3. Particle and gas-phase velocities were measured by laser Doppler velocimetry w ith particle size discrimination, and numerical simulations were carri ed out considering momentum exchange between both phases. Motion of sm all particles with Stokes number of around unity was influenced by str ong shear in the developing region. Streamwise turbulence intensity wa s Strongly attenuated by the addition of particles in the free shear l ayer region, while transverse turbulence intensity was suppressed in t he fully-developed region of both the free and wall shear regions. Mod ifications of the mean fluid velocity by the particles induced reducti on in the Reynolds stress, which alters the turbulence production. Tur bulence modification by particles, with Stokes number of order of unit y, is due primarily to the extra dissipation which is a function of pa rticle mean concentration and fluid turbulence in the fully-developed region.