The one-dimensional shallow water equations were modified for a Venturi contraction and expansion in a rectangular open channel to achieve more accurate results than with the conventional one-dimensional shallow water equations. The wall-reflection pressure-force coming from the contraction and the expansion walls was added as a new term into the conventional shallow water equations. In the contraction region, the wall-reflection pressure-force acts opposite to the flow direction; in the expansion region, it acts with the flow direction. The total variation diminishing scheme and the explicit Runge-Kutta fourth-order method were used for solving the modified shallow water equations. The wallreflection pressure-force effect was counted in the pure advection term, and it was considered for the calculations in each discretized cell face. The conventional shallow water equations produced an artificial flux due to the bottom width variation in the contraction and expansion regions. The modified shallow water equations can be used for both prismatic and nonprismatic channels. When applied to a prismatic channel, the equations become the conventional shallow water equations. The other advantage of the modified shallow water equations is their simplicity. The simulated results were validated with experimental results and three-dimensional computational fluid dynamics result. The modified shallow water equations well matched the experimental results in both unsteady and steady state.

This paper describes the results from simulations of laminar burning velocities in the premixed air and flammable gases vented from abused Li-ion batteries. The released mixture from such batteries contain mixtures of hydrogen, methane, ethylene, carbon monoxide and carbon dioxide. The study also includes the combustion properties of an electrolyte, dimethyl carbonate. The simulation results show the laminar burning velocities as a function of concentration, pressure and temperature for the gas mixtures and electrolyte. The goal of the present project is to use the simulated burning velocities in curve fitted functions for use in computational fluid dynamics (CFD) codes.

An experimental study of turbulent combustion of hydrogen sulfide (H 2 S) and natural gas was performed to provide reference data for verification of CFD codes and direct comparison. Hydrogen sulfide is present in most crude oil sources, and the explosion behaviour of pure H 2 S and mixtures with natural gas is important to address. The explosion behaviour was studied in a four-meterlong square pipe. The first two meters of the pipe had obstacles while the rest was smooth. Pressure transducers were used to measure the combustion in the pipe. The pure H 2 S gave slightly lower explosion pressure than pure natural gas for lean-to-stoichiometric mixtures. The rich H 2 S gave higher pressure than natural gas. Mixtures of H 2 S and natural gas were also studied and pressure spikes were observed when 5% and 10% H 2 S were added to natural gas and also when 5% and 10% natural gas were added to H 2 S. The addition of 5% H 2 S to natural gas resulted in higher pressure than pure H 2 S and pure natural gas. The 5% mixture gave much faster combustion than pure natural gas under fuel rich conditions.

Drilling for oil and gas is a complex process, involving pumping of fluid through kilometers of pipes. Even though the drilling fluid has a high speed of sound (≈1000 m/s), the large lengths involved make pressure wave propagation significant in timescales where such phenomena can usually be neglected in other processes. Managed pressure drilling, a technological extension of conventional drilling, adds a choke on the return flow from the drilling process. Significant work has been done in recent years on creating a simplified model of the process, often by neglecting distributed dynamics, and using this for controller design. This paper compares the simplified model most often used, with a distributed partial differential equation (PDE) model and compare the performance with measured data for wave propagation while doing managed pressure drilling. Fluid structure interaction and theoretical vs recorded speed of sound are discussed.

The present study compares two twin-fluid atomizer concepts based on the airflow (shock waves) pattern obtained through shadowgraph imaging for atomization of water with a low air/water pressure supply. The research work was conducted using the backlight imaging technique for converging (sonic) and converging–diverging (supersonic) air-assist atomizers with a 3.0 mm (throat) diameter. An annular sheet of thicknesses 70 µm and 280 µm with a high-speed air-core was employed to study the breakup dynamics for different water mass flow rates (100–350 kg/h) and air mass flow rates (5–35 kg/h). Different sheet breakup patterns were identified as the function of the ALR ratio (air-to-liquid mass flow), liquid Weber number (WeL), and Reynolds number (Reg). Different breakup modes extend from canonical Rayleigh bubble breakup, ligament-type breakup, to the pure pulsating breakup via annular sheet disintegration. The sheet breakup dynamics were studied in terms of spray angle and breakup length. With higher ALR values, breakup length showed a decreasing trend, while spray angle showed an increasing trend in the converging and converging–diverging (CD) air-assist atomizers, respectively, owing to the drastic difference in the jet flow dynamics.