Search results for "Laminar Flow"
showing 10 items of 78 documents
Testing a theoretical resistance law for overland flow under simulated rainfall with different types of vegetation
2020
Abstract In this paper a recently theoretically deduced flow resistance equation, based on a power-velocity profile, was tested using data collected for overland flow under simulated rainfall carried out in plots with vegetation. The available data were obtained exploring a wide range of rainfall intensities (from 60 to 181 mm h−1) and slopes (from 3.6 to 39.6%), and with four different types of vegetation. The database, including measurements of flow velocity, water depth, cross sectional flow area, wetted perimeter and bed slope, was divided in four datasets (one for each vegetation type), which allowed the calibration of the relationship between the velocity profile parameter Γ, the slop…
Testing a theoretically-based overland flow resistance law by Emmett’s database
2021
Abstract The main aim of this paper was to test a recently theoretically deduced flow resistance equation, based on a power-velocity profile, using a wide database of available measurements carried out in laboratory and field experimental runs with overland flow under simulated rainfall. In comparison with previous calibrations and validations of this theoretically deduced flow resistance equation, the used database by Emmett is characterized by a wide range of rainfall intensities (from 79.2 to 303.5 mm h−1 for laboratory runs and from 178.3 to 215.9 mm h−1 for field investigations) and bed slopes (from 0.33 to 17% for laboratory runs and from 2.9 to 33.2% for field investigations). For th…
Application of a non linear local analysis method for the problem of mixed convection instability
2007
Abstract We consider the problem of laminar mixed convection flow between parallel, vertical and uniformly heated plates where the governing dimensionless parameters are the Prandtl, Rayleigh and Reynolds numbers. Using the method based on the centre manifold theorem which was derived from the general theory of dynamical systems, we reduce a three-dimensional simplified model of ordinary differential amplitude equations emanating from the original Navier-Stokes system of the problem in the vicinity of a trivial stationary solution. We have found that when the forcing parameter, the Rayleigh number, increases beyond the critical value Ra s , the stationary solution is a pitchfork bifurcation…
Development and Scale-Up of the Electrochemical Dehalogenation for the Synthesis of a Key Intermediate for NS5A Inhibitors
2015
The electrochemical 2-fold dehalogenation of a spirocyclopropane-proline derivative at leaded bronze was scaled-up in a divided batch-type electrolysis cell in good yield and excellent selectivity. The upscaling via a flow electrolysis cell was also successful. Conditions were elaborated employing a single cell passage for complete conversion. The keys here are the direct cooling of the cathode and ensuring a good laminar flow.
Computational fluid dynamics and its application to transport processes
2007
Fluid transport behaviour is of great importance within the chemical process industry and in biotechnology. The complexity of this behaviour, reflected in the nature of the fundamental partial differential equations which describe it analytically, means that it has to be treated by numerical methods. In this paper the basic equations are given, and the approaches necessary to treat laminar and turbulent flows are carefully explained. As digital computers have increased in size, so has the comprehensiveness of the problems which can be treated, and the development of typical computer programs is described. Problems of accuracy and experimental validation are also surveyed, and it is shown th…
On numerical simulation of electromagnetic field effects in the combustion process
2018
This paper deals with a simplified model taking into account the interplay of compressible, laminar, axisymmetric flow and the electrodynamical effects due to Lorentz force’s action on the combustion process in a cylindrical pipe. The combustion process with Arrhenius kinetics is modelled by a single step exothermic chemical reaction of fuel and oxidant. We analyze non-stationary PDEs with 6 unknown functions: the 3 components of velocity, density, concentration of fuel and temperature. For pressure the ideal gas law is used. For the inviscid flow approximation ADI method is used. Some numerical results are presented.
PANORMUS-SPH. A new Smoothed Particle Hydrodynamics solver for incompressible flows
2015
Abstract A new Smoothed Particle Hydrodynamics (SPH) solver is presented, fully integrated within the PANORMUS package [7] , originally developed as a Finite Volume Method (FVM) solver. The proposed model employs the fully Incompressible SPH approach, where a Fractional Step Method is used to make the numerical solution march in time. The main novelty of the proposed model is the use of a general and highly flexible procedure to account for different boundary conditions, based on the discretization of the boundary surfaces with a set of triangles and the introduction of mirror particles with suitable hydrodynamic properties. Both laminar and turbulent flows can be solved (the latter using t…
Investigation of flow and heat transfer in corrugated passages—II. Numerical simulations
1996
An experimental and numerical study of flow and heat transfer was conducted for a crossed-corrugated geometry, representative of compact heat exchangers under transitional and weakly turbulent conditions. Three-dimensional numerical predictions were obtained by a finite volume method using a variety of approaches ranging from laminar flow assumptions to standard and low-Reynolds number k-e turbulence models, direct simulation, and large-eddy simulation. In this paper, the various computational approaches are presented and their relative performance is discussed for various geometries and Reynolds numbers; results are compared with experimental measurements and literature data. Detailed expe…
Heat transfer and flow resistance for stacked wire gauzes: Experiments and modelling
2012
Abstract The study deals with the flow resistance and heat transport properties of woven and knitted wire gauzes stacked in a tubular apparatus. The experimental programme included flow resistance and heat transfer experiments performed for air flow ( Re = 2–300) using three woven gauzes and one knitted gauze. During the heat transfer experiments, the gauzes were heated by electric current flowing directly through them. The models describing the flow resistance and the heat transfer were put forward. Both the models base on the concept of the laminar flow developing in a short capillary channel (i.e. the gauze mesh). The model describing the flow resistance does not contain the experimenta…
On natural convection in a single and two zone rectangular enclosure
1992
Abstract Convective heat transfer was investigated numerically for rectangular enclosures both undivided and divided in two zones by a vertical partition, and having opposite isothermal walls at different temperatures. The aspect ratio was varied from 0.1 to 16 and the Rayleigh number from 3.5 ∗ 10 3 to ∗ 10 7 (non-partitioned enclosures) and from 1.0 ∗ 10 5 to 1.6 ∗ 10 8 (partitioned enclosures). The thickness and conductivity of the partition were varied. The end wall thermal boundary conditions were adiabatic or LTP (Linear Temperature Profile). The continuity, momentum and energy equations for a 2-D laminar steady flow were solved under the Boussinesq approximation by using a finite-dif…