Chemical Process Simulation

Large Eddy Simulation of Liquid Plunging Jets Processes.

Chemical process simulation has several industrial applications such as chemical reactors, wastewater treatment, poring motion of liquid metal or glass and nuclear industry. It is considered as a desirable phenomenon in the case of wastewater treatment, for example, to promote the oxidization of the organic content.

However, it becomes an undesirable phenomenon in another chemical reaction simulator cases such as the activation of emergency core cooling (ECC) of a nuclear reactor in a loss of coolant accident for which the entrained air can affect heat transfer seriously.

Large Eddy Simulations, in conjunction with VOF interface tracking algorithm for weakly and highly disturbed liquid plunging jets, were conducted including the region of free jet development prior to impact, the initial impact phase, and the subsequent continuous entrainment phase.

The dynamic Smagorinsky-Lilly model under Favre-averaging of the Navier-Stokes equations solved using the commercially available chemical process simulation software ANSYS FLUENT 14.0.  The VOF approach used the continuous surface force (CSF) model which is commonly used in electrochemistry simulation (IL).  16.4 million computational cells were used and the resulting mesh was assessed based on LES requirements and bubble size distribution.  Boundary conditions were monitored to ensure a stable and fixed free surface of the liquid pool.  The integration time step was assessed based on characteristics of the flow studied such as the rising velocity of bubbles. The chemical process simulations were performed on the High-Performance Computing Cluster using 32 parallel processors for each case simulated.  The average computational time equal to 3583 hours to simulate 1s of physical time.  Two jets were considered; the rough jet was generated by a fully developed pipe flow while the smooth jet was generated by a flat velocity profile.  Experiments, for the rough jet, were conducted as well.

The main differences between smooth and rough jets were elucidated. The rough jet showed surface instabilities and sinuous movement playing a key role in the entrainment of air into the liquid pool.

During the continuous entrainment, the interfacial area evolution of both jets exhibited similar trends although that of the rough jet was largely higher than that of the smooth jet. As a consequence, the air entrainment rate for the rough jet was noticeably larger than that of the smooth jet (almost double).

Among the achievements of the research work was the successful prediction of the dimensions of the initial cavity and the bubble plume established once the continuous entrainment regime was reached.

The scope of this Combustion Modeling project is to develop the CFD Fire Dynamics Simulation (FDS) methods to predict the aero-thermal CTQs for GE Aviation and Power combustors using high fidelity combustion and turbulence models.