Thermal stresses due to a hot-air jet impinging on a glass sheet can be used to stably initiate and attract a crack toward the jet axis. Relative motion between the jet and glass sheet then can be used to cut the glass sheet. This paper presents a theoretical and experimental study of this process for straight cuts. The model consists of sequentially coupled thermal and stress analyses for different cutting velocities. The stress field is used to compute stressintensity factors for different assumed positions of a crack behind the moving air jet. The minimum air temperature for cutting and the stand-off distance of the crack behind the nozzle increase as the cutting velocity increases. The various process and material parameters that control the process-including cutting speed, air temperature, and sheet thickness-are reduced to dimensionless numbers. Theoretical results, presented as a map in the space of these dimensionless numbers, describe the conditions under which cutting is possible. An experimental cutting apparatus has been constructed and used to validate the heattransfer analyses. Cutting experiments on this apparatus are in good agreement with the model.

High pressure superheated or saturated steam line breaks in a nuclear power plant generate high speed jet flows and blast waves. The jet loads and blast wave pressures can damage critical nuclear power plant components. An accurate assessment of these effects including uncertainty quantification (UQ), is essential to confirm that design is robust enough to handle jet flows and blast waves from postulated steam line breaks. This paper presents the verification and validation of a computational model created using a commercial CFD code for making such assessments. The verification and validation process involves the steps of application space parametrization, Phenomena Identification and Ranking (PIR), CFD model lockdown, selection of validation dataset, and calculation of formal validation metrics. The Uncertainty Quantification in the actual application should include the propagated validation uncertainties from the validation test problems.

The assessment of liquid flow patterns forming due to a submerged pump intake, and its associated gas entrainment phenomena, need to be reliable and accurate for a number of design applications. The use of conservative correlations can lead to gross over-design or, inaccurate predictions in certain complex suction arrangements. Scale model testing often has scale effects which leads engineers to rely on other analysis methods. Simplified analyses can fail to correctly predict the vortical features near the suction intakes and associated gas entrainment, which may lead many applications to use Computational Fluid Dynamics (CFD) as a method for intake flow predictions. However, reliable assessment of gas entraining into a suction intake with high Reynolds number internal flow, involves several physical modeling and numerical challenges. An accurate assessment requires, (1) a transient model, (2) proper resolution in the wall boundary layers near the intakes, (3) resolution of the swirl in the vortical structures, and (4) modeling of the laminar-to-turbulent transitional effects in the vicinity of the intake. This paper addresses and evaluates the performance of several turbulence model options and modifications within a CFD code for the assessment of intake flow. The results presented in this paper, are compared against published experimental data on vortical flow patterns at intakes, to identify physical and numerical modeling needs for such assessments. The results show that while, adequately resolved meshes, and low Reynolds number RANS (Reynolds Averaged Navier Stokes) turbulence models can capture the location and relative strength of vortices, the results for flow details inside the vortical structures identified need to be interpreted carefully, considering the relevant flow physics and modeling limitations. The turbulence model modifications proposed involve curvature correction and scale adaptiveness.

In designing propane quenching systems, a number of concerns arise with the specific fluids properties, thermal, and structural behavior of the system. In this work, the fluid-based loading on a quenched piping system is examined using computational fluid dynamics (CFD). Fluids loading is assessed during an event when a propane line is liquid quenched prior to a recycle valve opening event. During the event, hot vaporous propane is quickly exhausted into the quenched pipe. The CFD studies suggest that the loading in such an event is much larger than a similar event where the line is not quenched. Several aspects of the quench are shown to increase the loads with respect to the non-quench line, and appear to be associated with two mechanisms. The first load amplifying mechanism is the reduction of sound speed in a liquid/vapor mixture. This effect impacts the axial load in the pipe, and increases it multiple orders of magnitude as compared to a pure vapor flow. The second load increasing mechanism observed was due to slug formation. It was found that when considering quench stream droplets, stratification layers are likely to develop eventually within long pipes as the velocity from the nozzles is dissipated in the large line. In the pipe investigated, the hot, high-speed vapor blows the stratified liquid into a slug. When the slug makes turns through elbows, the pipe axial load increased even more. Simultaneously, a similar scale, perpendicular load was also observed. The overall results suggest that these loading events are not small and should be considered in the structural design and layout of a quenching system. The series of results also indicates that CFD provides a valuable tool for assessing complex two phase fluid issues, in particular for the loading on a pipe.

During the startup of a new fossil power plant, a high level of fly ash accumulation (higher than predicted) was encountered in the flue gas ducting upstream of a fluidized bed scrubber. The level of fly ash accumulation made it necessary to manually withdraw fly ash using a vacuum truck after short periods of operation, at less than 80% maximum continuous rating (MCR). This paper presents a simple method for rapid assessment of fly ash accumulation in flue gas ducts using steady state single phase Computational Fluid Dynamics (CFD) simulation of flue gas flow. The propensity for fly ash accumulation in a duct is predicted using calculated wall shear stresses from CFD coupled with estimates for the critical shear stresses required for mobilization of settled solids. Critical values for the mobilization stresses are determined from the Shields relations for incipient motion of particles in a packed bed with given fly ash particle size and density as inputs. Solids accumulation is possible where the wall shear stress magnitude is less than the critical shear stress for mobilization calculated from the Shields relations. Predictions of incipient fly ash accumulation based on the coupled CFD/Shields relations model correlate well with plant startup field observations. Fly ash accumulation was not observed in a related physical scale model test. A separate CFD/Shields relation analysis of the scale model physical tests show that the wall shear stresses in the scale model are several times larger than the critical value required for the mobilization of the fly ash simulant. This study demonstrates that a simple steady state, single phase CFD analysis of flue gas flow can be used to rapidly identify and address fly ash accumulation concerns in flue gas duct designs. This approach is much simpler and computationally inexpensive compared to a transient Eulerian multiphase simulation of particle laden flow involving handling the dense phase in regions of ash accumulation. Further, this study shows that physical model tests will be accurate for predicting fly ash accumulation, only if, the scaling maintains the proper ratio of wall shear stress to critical remobilization stress.