The Test Research Of Velocity Field On The Level Swirling Flow Spillway Tunnel

The spiraling flow has many merits, such as easy construction, flexible arrangement, high energy dissipation, basically to avoid many problems brought by the high-speed currents, so the relevant study has important theoretical meaning and practical application value.Through the model test and theoretical analysis, based on the relevant hydraulic physics measure, this paper researches the distribution law of velocity and the wall pulse pressure in the level spiraling flow spillway tunnel, at the same time, studies and analyzes the law of discharge, the partition of typical flow patterns, the distribution of wall time average pressure. Research results include the following aspects. The first use of laser-doppler anemometer (LDA) carries the velocity measurements on the level spiraling flow spillway tunnel, the study found, the distribution of axis velocity along radius direction may be seen as secondary curve which the maximum near the wall, tangent velocity shows composite swirl distribution, that is near the pipe center shows force swirl distribution, and near the wall shows free swirl distribution. With the swirl decays along the tunnel the highest point moving to the pipe center; With the upstream water level reducing and the downstream water level increasing, the highest tangent velocity also moving to the pipe center. The paper also studies the law of pulse velocity and turbulence intensity, along the radius, along the tunnel and with the flow patterns, analyzes the impact of changing speed and turbulence intensity of the main factors.Through the research of wall pulse pressure, the basic frequency is in 0.03~1.6Hz, which belongs to the low frequency scope, far from the building natural frequency, so the flow pulsation cannot resonate with the building; The pulsation energy, that is the pulsation dominant frequency, mainly concentrates between 0 ~ 20Hz. With swirl decays the various measuring points frequency along the tunnel also corresponding weaken. The distribution of wall pulsation pressure amplitude probability of level spiraling flow spillway tunnel basically presents the Gauss normal distribution; In the head(Z/D=0 ~ 4.5) and tail (Z/D=29 ~ horizontal section export) of horizontal section, because of the influence from the non-constant flow, the Cs, Ce are slightly bigger than theoretical value.The paper researches and analyzes the basic flow pattern sequence, the transitional flow characteristics and critical hydro conditions. The typical flow is divided into four basic flow position. .The wall pressure of level spiraling flow spillway tunnel is mainly constitute by the centrifugal force , the gas pressure in the cavum and the downstream water level measured pressure. In the range of Z/D=0~4.5, it exists potential energy transforming into kinetic energy, so the time average pressure has some fluctuations, the change law is different with the flow patterns. After the transition of the hole to the level exports, the time average pressure is reduced along the tunnel by the law of (P/D) =ALn (Z/D) +B.