Experimental investigation of the thermal-hydraulics of gas jet expansion In a two-dimensional liquid pool

"October 1978."Also issued as an M.S. thesis by the first author and supervised by the second author, MIT Dept. of Nuclear Engineering, 1978Includes bibliographical references (pages 115-117)Gas jet blowdown in a two-dimensional liquid pool has been experimentally investigated. Two sets of experiments were performed: a set of hydrodynamic experiments, where a non-condensible gas is injected into a subcooled liquid pool; and a set of thermal-hydraulic experiments, where a non-condensible heated gas is injected into a near saturated liquid pool. Liquid entrainment by the gas, bubble growth characteristics, and the potential for vaporization, were investigated for a variety of experimental pressures (3 to 10 bars) and two liquid types (water and R-113). Liquid entrainment increased with increasing pressure. The fraction of the jet volume which is liquid is relatively the same for all pressures and decreases with time of expansion. A Taylor instability mechanism for entrainment is found to under predict the entrained volume. In the initial stages of the expansion, higher entrainment is experienced for more dense fluids. For the same fluid, the entrainment rate was slightly higher for the heated experiments compared to the unheated experiments. Both lateral and vertical growth rates increased with pressure. Vaporization may have occurred for the 4 bar initial pressure, 12 °C superheat condition in freon R-113.Report issues under contract with the U.S. Nuclear Regulatory Commission NRC-04-77-12

Mass shedding rate of an isolated high-speed slug propagating in a pipeline

An isolated liquid slug in the pipeline can accelerate and achieve a high speed when subjected to a driving pressure. During the slug’s high-speed movement in a pipeline, part of the liquid will shed from it resulting in changes in the slug’s mass and length. To understand the mass shedding mechanism, the mass shedding rate is studied using three-dimensional computational-fluid-dynamics methodology, in which the volume-of-fluid technique is applied to track the water–air interface and the RNG (Formula presented.) model is used to describe the turbulence. The effects of driving pressure, initial slug length, pipe inclination angle, pipe wall roughness and gravity on the slug mass shedding rate are investigated. The results show that the slug mass shedding rate is independent of driving pressure, initial slug length, pipe inclination angle and gravity, and it increases as a power function with the increase in wall roughness. It is explained from the mass shedding rate that when the slug’s traveled distance exceeds six times the initial slug length, the slug will break up. This paper solves the problem that there is no standard to select a reliable mass shedding rate for modeling the isolated high-speed slug propagating in pipelines. Highlights: Simulate the movement of an isolated liquid slug propelled by pressurized air with 3D CFD model. Propose a model for calculating the slug mass shedding rate. Study three influence factors of the slug mass shedding rate.</p

Simulating unsteady conduit flows with smoothed particle hydrodynamics

Pipelines are widely used for transport and cooling in industries such as oil and gas, chemical, water supply and sewerage, and hydro, fossil-fuel and nuclear power plants. Unsteady pipe flows with large pressure variations may cause a range of problems such as pipe rapture, support failure, pipe movement, vibration and noise. The unsteady flow is generally caused by flow velocity changes due to valve or pump operation. Water hammer is the best known and extensively studied phenomenon in this respect. Fast transient may also occur in rapid pipe filling and emptying processes. Due to high driving heads, the advancing liquid column may achieve a high velocity. When this high-velocity column is blocked or restricted in its flow, high water-hammer pressures may result. Another scenario is that of slug flow, which arguably is the most dangerous type of two-phase pipe flow. Heavy isolated liquid slugs travelling at high speed behave like cannonballs. Damage is likely to happen when these slugs impact on barriers such as pumps, bends and partially closed valves. Advancing liquid columns occurring in rapid pipe filling and emptying can be seen as a special case of isolated slugs. In this thesis, we present a Lagrangian particle method for solving the Euler equations with application to water hammer, rapid pipe filling and emptying, and isolated slugs travelling in an empty pipeline. As a meshfree method, the smoothed particle hydrodynamics (SPH) used herein is suitable for problems encompassing moving boundaries and impact events, which are the common features of the concerned topics. We first present the kernel and particle approximation concepts, which are two essential steps in SPH. Based on numerical approximation rules, the SPH discrete form of the Euler and Navier-Stokes equations are derived. To treat various boundary conditions, we apply several types of image particles that are particularly designed to complete the kernels truncated by system boundaries. The global conservation of mass and linear momentum is then demonstrated. The SPH errors in the integral approximation and summation approximation are analyzed based on given particle distribution patterns. Several other problems such as particle clustering, tensile instability, particle boundary layer and lacking of polynomial reproducing abilities (incompleteness) are also discussed together with possible remedies. Before applying the implemented particle solver to the thesis topics, we first thoroughly test it against a selection of two-dimensionale benchmarks, which have close relationship with the concerned problems. They include dam-break, jet impinging onto an inclined plane, emerging jet under gravity, free overfall and flow separation at bends. Good agreements with analytical and numerical solutions in literature are found. The convergence rate of SPH is shown to be of first order, which is consistent with the theoretical analysis. For the rapid pipe filling problem, we apply the 1D SPH solver to the experiment of Liou &amp; Hunt [114]. The velocity head at the inlet has to be taken into account to obtain a good agreement with the experiment. Water elasticity does not play a role and the friction formulation for steady state flows can be used. Head transition analysis provides deeper insight into the hydrodynamic behaviour in the filling process. As a special case of pipe filling, water hammer due to liquid impact at partially and fully closed valves is studied. The results agree well with standard MOC solutions. Similar observations are made for the rapid emptying process. For the isolated slug travelling in a voided pipeline and impacting on a bend, we apply the 1D and 2D SPH solvers to the experiments of Bozkus [24]. To obtain the arrival velocity of the slug at the elbow, a 1D model including mass loss at the slug tail is used. In the slug impact, flow separation at the bend plays a vital role, which is typical 2D flow behaviour at a geometrical discontinuity. With the flow contraction coefficient obtained from 2D SPH solutions, the improved 1D model gives good results for the reaction force, not only in magnitude but also its duration and shape. Finally, to study the evolutions of air/water interface and its possible effect on filling and emptying processes, a new experimental study is performed in a large-scale pipeline. It is found that in filling the water front tends to split into two fronts propagating with different velocities. This results in air intrusion on top of a water platform. In emptying, flow stratification occurs at the water tail. Consequently, the validated assumption of vertical air/water interfaces for small-scale system with high driving head may not be applicable to large-scale systems. The interface evolution does not play an important role in pipe filling, the overall behaviour of which can be well predicted with 1D SPH solutions. However, flow stratification largely affects the overall draining process

The hydrodynamics of an individual transient slug in a voided line

Thesis (Ph. D.)--Michigan State University. Department of Civil and Environmental Engineering, 1991Includes bibliographical references (pages 117-121

Contamination Control Handbook for Ground Fluid Systems Final Technical Publication

Handbook for contamination control of aerospace ground fluid systems and portable equipmen

Diagnosis of condensation induced waterhammer methods and background

This guidebook provides reference material and diagnostic procedures concerning condensation-induced waterhammer in nuclear power plants. Condensation-induced waterhammer is the most damaging form of waterhammer and its diagnosis is complicated by the complex nature of the underlying phenomena. In Volume 1, the guidebook groups condensation-induced waterhammers into five event classes which have similar phenomena and levels of damage. Diagnostic guidelines focus on locating the event center where condensation and slug acceleration take place. Diagnosis is described in three stages: an initial assessment, detailed evaluation and final confirmation. Graphical scoping analyses are provided to evaluate whether an event from one of the event classes could have occurred at the event center. Examples are provided for each type of waterhammer. Special instructions are provided for walking down damaged piping and evaluating damage due to waterhammer. To illustrate the diagnostic methods and document past experience, six case studies have been compiled in Volume 2. These case studies, based on actual condensation-induced waterhammer events at nuclear plants, present detailed data and work through the event diagnosis using the tools introduced in the first volume. 65 figs., 8 tabs. Document type: Repor