An emergency response model for evaluating the formation and dispersion of plumes originating from major fires (BUOYANT v4.20)

A mathematical model called BUOYANT has previously been developed for the evaluation of the dispersion of positively buoyant plumes originating from major warehouse fires. The model addresses the variations of the cross-plume integrated properties of a rising plume in a vertically varying atmosphere and the atmospheric dispersion after the plume rise regime. We have described in this article an extension of the BUOYANT model to include a detailed treatment of the early evolution of the fire plumes, before the plume rise and atmospheric dispersion regimes. The model input and output consist of selected characteristics of forest or pool fires, and the properties of a source term for the plume rise module, respectively. The main model structure of this source term model is based on the differential equations for low-momentum releases of buoyant material, which govern the evolution of the plume radius, velocity and density differences. The model is also partially based on various experimental results on fire plumes. We have evaluated the refined BUOYANT model by comparing the model predictions against the experimental field-scale data of the Prescribed Fire Combustion and Atmospheric Dynamics Research Experiment, RxCADRE. The predicted concentrations of CO2 agreed fairly well with the aircraft measurements conducted in the RxCADRE campaign. We have also compiled an operational version of the model. The operational model can be used for emergency contingency planning and for the training of emergency personnel, in case of major forest and pool fires.

Source term model of radioactive liquid spills for actual decision support systems

Spills of liquid radioactive material are reviewed as potential event that can be associated with release into the atmosphere. Existing approaches to radiological impact assessment for onsite as well as offsite of facility are presented. The example of using the actual Java version of the European RODOS system as prototype of the decision support system shows the general implementation of the analysis and preparation of initial data in order to model the radiological impact on the public, personnel and environment. Given the specifics of the occurrence of emergency scenarios of this type, features of atmospheric models application, description of the source term model, software integration features, ventilation task solving, completeness and format of the initial data required for radiological consequence modelling.

Non-Uniform Source Term Model for Film Cooling With the Internal Cross Flow

The source term model is an effective way to reduce the calculation consumption in predicting film cooling performance. The aim of this work is to develop a new source term model to consider the non-uniform in-hole flows. The internal cross flow that occurs in air-cooled blades and vanes has been shown to distinctly affect the cooling performance. In this work, the in-hole flow mechanism with the presence of the internal cross flow is studied. A topological model that divides in-hole flows into three parts and several regions is put forward. It is shown that, compared with the parallel ones, the perpendicular internal cross flows dominate the cooling performance. What is more, flows within the cooling hole are not affected by the main flow, especially in the region under a certain plane (named the R plane). This feature makes it possible for a source term model to work under various main flow conditions. Based on these understandings, a non-uniform source term model is established. It models and solves the three-dimensional in-hole flows by a two-dimensional transient solver and describes the effect of the internal cross flow as initial conditions using a vortex model. The result of the transient solver is then transformed into the axial velocity distribution at the R plane and is used as the source term. The prediction of the source term model is compared with full CFD under various VR, VRi and β, showing the ability of this model to predict the effect of the internal cross flow with discrepancy increasing with VR. Accurate modeling of the three-dimensional in-hole flows is the key point in this source term model and needs further development.

jBAY Modeling of Vane-Type Vortex Generators and Study on Airfoil Aerodynamic Performance

The increased demand for wind power is related to changes in the sizes of wind turbines and the development of flow control devices, such as vortex generators (VGs). In the present study, an analysis of the vortices generated by a vane-type VG is performed. To that end, the aerodynamic performance of a DU97W300 airfoil with and without VG is evaluated. The jBAY source term model was implemented for simulation of a triangular-shaped VG and the resolution of the fully meshed computational fluid dynamics (CFD) model. Reynolds-averaged Navier–Stokes (RANS) based simulations were used to calculate the effect of VGs in steady state, and the detached eddy simulation (DES) method was used for angles of attack (AoAs) around the stall situation. All jBAY based numerical simulations were carried out with a Reynolds number of Re = 2 × 106 to analyze the influence of VGs with AoAs between 0 and 20° and were validated versus experimental wind tunnel results. The results show that setting up a VG device on an airfoil benefits its aerodynamic performance and that the use of the jBAY model for simulation is accurate and efficient.

Source term model for rod vortex generator

Purpose The simulations of grid-resolved rod vortex generators (RVGs) require high computational cost and time. Additionally, the computational mesh topology must be adjusted to rods geometries. The purpose of this study is to propose the new source term model for RVG. Design/methodology/approach The model was proposed by modification of Bender, Anderson, Yagle (BAY) model used to predict flows around different type of vortex generators (VGs) – vanes. Original BAY model was built on lifting line theory. The proposed model was implemented in ANSYS Fluent by means of the user-defined function technique. Additional momentum and energy sources are imposed to transport equations. Findings The computational results of source term model were validated against experimental data and numerical simulation results for grid-resolved rod. It was shown that modified BAY model can be successfully used for RVG in complex cases. An example of BAY model application for RVG on transonic V2C airfoil with strongly oscillating shock waves is presented. Aerodynamic performance predicted numerically by means of both approaches (grid resolved RVG and modeled) is in good agreement, what indicates application opportunity of the proposed model to complex cases. Practical implications Modified BAY model can be used to simulate the influence of RVGs in complex real cases. It allows for time/cost reduction if the location or distribution of RVG has to be optimized on a profile, wing or in the channel. Originality/value In the paper, the new modification of BAY model was proposed to simulate RVGs. The presented results are innovative because of original approach to model RVGs.

A triangular vortex generator modeling on a DU97-W-300 airfoil by a source term model

Vortex generators are passive devices employed to improve the aerodynamic performance of aircraft and wind turbine blades. More concretely, these devices have high potential in improving the power output of wind turbines that are producing less power than expected. Besides, it can improve the aerodynamic performance of the nearest parts to the rotor of turbine blades that usually enter in stall. The main goal of this article is to model the triangular vortex generator effect on a DU97-W-300 airfoil by a source term model. This is aimed by comparing the lift and drag coefficients from experimental studies with the data obtained in the computational fluid dynamics study. Furthermore, the vertical path and the size and strength of the vortex are studied for different angles of attack in order to see how the vortex genertaor behaves in different conditions.