scholarly journals The lifting force of an airplane wing when flying horizontally at high speeds. Explanation of the vortex trail.

2021 ◽  
Author(s):  
Alexander Braginsky
Keyword(s):  
High Speed ◽  
Continuous Medium ◽  
Navier Stokes ◽  
Potential Force ◽  
Navier Stokes Equation ◽  
Lifting Force ◽  
High Speeds ◽  
Horizontal Flight ◽  
Airplane Wing ◽  
Force Potential

Abstract In this paper, an explanation is given of the lift force of an airplane during horizontal flight. It is shown that during a flight, five vertical forces act on the airplane: gravity; pressure gradient with a minus sign; Archimedes force; potential force and the vortex force obtained from the action minimum. The first three forces were known before. The potential force was also known from the Bernoulli equation, but its effect on the airfoil from the air had not previously been taken into account. The vortex force obtained from the minimum action in the application to a continuous medium was not taken into account in aerodynamics. In horizontal flight the vortex force is directed upwards, it compensates for the gravity of the airplane at high speed commensurate with the speed of sound. The paper provides an explanation of the vortex trail behind the airplane, mentioned in the Millennium problem Navier-Stokes equation.

scholarly journals The Lifting Force of An Airplane Wing When Flying Horizontally at High Speeds.

2020 ◽  
Author(s):  
Alexander Braginsky
Keyword(s):  
High Speed ◽  
Lift Force ◽  
Continuous Medium ◽  
Potential Force ◽  
Lifting Force ◽  
High Speeds ◽  
Horizontal Flight ◽  
Airplane Wing ◽  
Archimedes Force ◽  
Force Potential

Abstract In this paper, an explanation is given of the lift force of an airplane during horizontal flight. It is shown that during a flight, five vertical forces act on the airplane: gravity; pressure gradient with a minus sign; Archimedes force; potential force and the vortex force obtained from the action minimum. The first three forces were known before. The potential force was also known from the Bernoulli equation, but its effect on the airfoil from the air had not previously been taken into account. The vortex force obtained from the minimum action in the application to a continuous medium was not taken into account in aerodynamics. In horizontal flight the vortex force is directed upwards, it compensates for the gravity of the airplane at high speed commensurate with the speed of sound. The article provides an explanation of the vortex trail behind the airplane, mentioned in the CMI Millennium problem.

COMPARISON OF UNSTEADY REYNOLDS-AVERAGED NAVIER-STOKES PREDICTION OF SELF-PROPELLED CONTAINER SHIP SQUAT AGAINST EMPIRICAL METHODS AND BENCHMARK DATA

2021 ◽  
Vol 162 (A2) ◽  
Author(s):  
Z Kok ◽  
J T Duffy ◽  
S Chai ◽  
Y Jin
Keyword(s):  
Water Depth ◽  
High Speed ◽  
Navier Stokes ◽  
Container Ship ◽  
Benchmark Data ◽  
High Speeds ◽  
Port Throughput ◽  
Finite Water Depth ◽  
Urans Cfd ◽  
Effective Wake

The demand to increase port throughput has driven container ships to travel relatively fast in shallow water whilst avoiding grounding and hence, there is need for more accurate high-speed squat predictions. A study has been undertaken to determine the most suitable method to predict container ship squat when travelling at relatively high speeds (Frh ≥ 0.5) in finite water depth (1.1 ≤ h/T ≤ 1.3). The accuracy of two novel self-propelled URANS CFD squat model are compared with that of readily available empirical squat prediction formulae. Comparison of the CFD and empirical predictions with benchmark data demonstrates that for very low water depth (h/T < 1.14) and when Frh < 0.46; Barass II (1979), ICORELS (1980), and Millward’s (1992) formulae have the best correlation with benchmark data for all cases investigated. However, at relatively high speeds (Frh ≥ 0.5) which is achievable in deeper waters (h/T ≥ 1.14), most of the empirical formulae severely underestimated squat (7-49%) whereas the quasi-static CFD model presented has the best correlation. The changes in wave patterns and effective wake fraction with respect to h/T are also presented.

Comparison of Unsteady Reynolds-Averaged Navier-Stokes Prediction of Self-Propelled Container Ship Squat Against Empirical Methods and Benchmark Data

2020 ◽  
Vol 162 (A2) ◽  
Author(s):  
Z Kok ◽  
J T Duffy ◽  
S Chai ◽  
Y Jin
Keyword(s):  
Water Depth ◽  
High Speed ◽  
Navier Stokes ◽  
Container Ship ◽  
Benchmark Data ◽  
High Speeds ◽  
Port Throughput ◽  
Finite Water Depth ◽  
Urans Cfd ◽  
Effective Wake

The demand to increase port throughput has driven container ships to travel relatively fast in shallow water whilst avoiding grounding and hence, there is need for more accurate high-speed squat predictions. A study has been undertaken to determine the most suitable method to predict container ship squat when travelling at relatively high speeds (Frh ≥ 0.5) in finite water depth (1.1 ≤ h/T ≤ 1.3). The accuracy of two novel self-propelled URANS CFD squat model are compared with that of readily available empirical squat prediction formulae. Comparison of the CFD and empirical predictions with benchmark data demonstrates that for very low water depth (h/T < 1.14) and when Frh < 0.46; Barass II (1979), ICORELS (1980), and Millward’s (1992) formulae have the best correlation with benchmark data for all cases investigated. However, at relatively high speeds (Frh ≥ 0.5) which is achievable in deeper waters (h/T ≥ 1.14), most of the empirical formulae severely underestimated squat (7-49%) whereas the quasi-static CFD model presented has the best correlation. The changes in wave patterns and effective wake fraction with respect to h/T are also presented.

scholarly journals Thermo-Elastohydrodynamic Study on Textured Journal Bearing with High-Speed and High-Specific-Pressure

2019 ◽  
Vol 37 (4) ◽  
pp. 751-756 ◽  
Author(s):  
Lin Wang ◽  
Yu Zhang ◽  
Guoding Chen
Keyword(s):  
Elastic Deformation ◽  
High Speed ◽  
Journal Bearing ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Specific Pressure ◽  
Analysis Model ◽  
Navier Stokes Equation ◽  
Gear Transmission System ◽  
Load Carrying

The performance of supporting journal bearing of the star gear transmission system in the geared turbo fan engine (GTF) is analyzed. A thermal-elastohydrodynamic analysis model was developed for textured journal bearing used in high-speed and high-specific-pressure conditions. The Navier-Stokes equation, energy equation, and viscosity-temperature equation were calculated by the computational fluid dynamics method. The influence of elastic deformation on bearing thermal hydrodynamic performance was studied in detail. The results indicate that the elastic deformation has an influence on the distribution of oil temperature and oil pressure. Besides, a comparative thermo-elastohydrodynamic analysis was conducted between the textured bearing and the un-textured bearing, and the discrepancies of maximum oil pressure, load carrying capacity and the maximum oil temperature are few. However, the textured bearing has a lower elastic deformation than the un-textured bearing.

A Transient CFD Simulation of the Flow in a Test Rig of an Aeroengine Bearing Chamber

2014 ◽  
Author(s):  
Akinola A. Adeniyi ◽  
Hervé P. Morvan ◽  
Kathy A. Simmons
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Film Formation ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Oil Film ◽  
Sheared Flow ◽  
Fine Mesh ◽  
Computational Overhead ◽  
Formation Pattern

In this paper, we present results for the application of an Eulerian-Lagrangian technique to the transient simulation of an oil film formation on the walls of an aeroengine bearing chamber. The flow of oil in an aeroengine bearing chamber consists of high speed oil droplets interacting with the bearing structures and flowing oil film. The situation in the chamber is highly rotational and consisting of sheared flow of air over oil. The bearing chamber may also be located in the vicinity of the combustion chamber. The oil provides lubrication and cooling of the hot structures. Modelling the flow in the bearing chamber is therefore complex. The Volume of Fluid (VoF) technique offers a potential platform to model droplet-film interaction; however, it requires fine mesh details to capture the flow to the droplet level. Such detailed resolution would not be practical for the complete chamber geometry because of the prohibitively expensive computational overhead requirements. A Lagrangian formulation is therefore proposed to represent the droplets as source terms in the Navier-Stokes equation while the film is represented using VoF. This effectively reduces the need to resolve the droplets explicitly. The predicted film formation pattern compares with experimental results.

The Effect of Flux Dysconnectivity Functions on Concentration Gradients Changes in a Multicomponent Model of Convectional Reaction-Diffusion by the Example of a Neurovascular Unit

2021 ◽  
Vol 413 ◽  
pp. 19-28
Author(s):  
Yaroslav R. Nartsissov
Keyword(s):  
Blood Flow ◽  
Fluid Flow ◽  
Blood Vessels ◽  
High Speed ◽  
Neurovascular Unit ◽  
Reaction Diffusion ◽  
Navier Stokes ◽  
Concentration Gradients ◽  
Navier Stokes Equation ◽  
Specific Trait

A convectional diffusion of nutrients around the blood vessels in brain occurs in well-structured neurovascular units (NVU) including neurons, glia and micro vessels. A common feature of the process is a combination of a relatively high-speed delivery solution stream inside the blood vessel and a low-speed convectional flow in parenchyma. The specific trait of NVU is the existence of a tight cover layer around the vessels which is formed by shoots (end-feet) of astrocytes. This layer forms so called blood-brain barrier (BBB). Under different pathological states the permeability of BBB is changed. The concentration gradient of a chemical compound in NVU has been modelled using a combination of mathematical description of a cerebral blood flow (CBF) and further 3D diffusion away from the blood vessels borders. The governing equation for the blood flow is the non-steady-state Navier–Stokes equation for an incompressible non-Newtonian fluid flow without buoyancy effects. BBB is modeled by the flux dysconnectivity functions. The velocity of fluid flow in the paravascular space was estimated using Darcy's law. Finally, the diffusion of the nutrient is considered as a convectional reaction-diffusion in a porous media. By the example of glucose, it was shown that increased permeability of BBB yields an increased level of the nutrient even under essential (on 70%) decrease of CBF. Contrarily, a low BBB permeability breeds a decreased concentration level under increased (on 50%) CBF. Such a phenomenon is explained by a smooth enlarge of the direct diffusion area for a blood-to-brain border glucose transport having three-level organization.

Three-dimensional surges and recoveries in a numerical glacier model

1969 ◽  
Vol 6 (4) ◽  
pp. 979-986 ◽  
Author(s):  
William J. Campbell ◽  
Lowell A. Rasmussen
Keyword(s):  
Steady State ◽  
High Speed ◽  
Three Dimensional ◽  
Volume Transport ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Navier Stokes Equation ◽  
Total Recovery ◽  
Flow Equations ◽  
Bed Friction

The Navier–Stokes equation, integrated vertically to yield a two-dimensional transport equation, is combined with the three-dimensional continuity equation. By assuming a linear relation between volume transport and bottom shear stress, a system of numerically tractable differential equations is developed that contains a nonlinear surface slope term and a term in which horizontal frictional forces are stated explicitly. These equations, which are not based on perturbation analysis, are integrated directly on a high speed digital computer. The coefficient of each term in the flow equations is composed of physical parameters (gravity, density, viscosity); therefore, since no quantities such as ice velocities enter the equations, it is only necessary to specify an arbitrary bed configuration and a net-balance versus altitude curve to obtain a glacier solution.For two beds, valley and cirque, steady-state glacier solutions are found for a variety of bed and lateral frictional values. By reducing the bed friction coefficient for one year over the entire bed of the glacier, surges are induced in each of these cases. A reduction in bed friction to 5% of its original value yields a surge resembling typical observed surges. Interesting wave forms occur during the recovery. During the initial recovery, after the bed friction has been restored to its original value, height falls continue to occur even in the lower accumulation zone. The original steady-state shape is approached asymptotically, with total recovery taking hundreds of years.

Numerical Study on Aerodynamic Performances of CRH3 under Crosswind

2012 ◽  
Vol 215-216 ◽  
pp. 992-997
Author(s):  
Hong Yuan Su ◽  
Ming Li ◽  
Dong Ping Wang ◽  
Feng Liu
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Lateral Force ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Aerodynamic Properties ◽  
Aerodynamic Performances ◽  
Volume Method ◽  
Incompressible Navier Stokes Equation ◽  
Multiple Units

Based on 3D steady and incompressible Navier-Stokes equation and standard k-ε turbulent model, numerical calculation for the aerodynamic properties of EMU (Electric Multiple Units) CRH3 (China Railway High-Speed 3)running in crosswind were carried out by finite volume method. Aerodynamic performances of EMU CRH3 were analyzed and compared, when the EMU was running in different speed and under the crosswinds of different velocity. The research showed that with the change of speed of train and crosswind, the surface pressure and aerodynamic forces altered according to a certain rule. Compared with the drag, the change of lift and lateral force caused by the increase of crosswind were more serious. When the speed of train was constant of 200km/h, 250km/h and 300km/h, the drag of train increased by 26.7%, 20.4% and 19.8% respectively as the speed of crosswind increased from 12.5m/s to 30m/s, the lift of train increased by 340.7%, 331.7% and 337.1% respectively, and the lateral force of train increases by 296.3%, 266.0% and 150.2% respectively. As the speed of crosswind increases, the increase of drag caused by the acceleration of train is more serious than lift and lateral force.

scholarly journals Prediksi Hambatan Kapal dengan Menggunakan Metode Overset Mesh pada Kapal Planing Hull

2020 ◽  
Vol 4 (1) ◽  
pp. 24-34
Author(s):  
Abubakar Fathuddiin ◽  
Samuel Samuel ◽  
Kiryanto Kiryanto ◽  
Aulia Widyandari
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Volume Of Fluid ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ship Resistance ◽  
High Speeds ◽  
Mesh Method ◽  
Reynolds Averaged Navier Stokes ◽  
Volume Method

ABSTRAKPrediksi hambatan kapal tipe planing lebih rumit dibanding dengan tipe displacement, hal ini disebabkan oleh gaya hidrodinamis yang lebih dominan pada bagian bawah kapal. Karakteristik hambatan kapal tipe planing sangat dipengaruhi oleh gerakan trim dan heave. Selain itu, bentuk hullform juga mempengaruhi hambatan kapal; seperti sudut dead-rise, chine, strip, stephull, dan lain-lain. Solusi untuk memprediksi hambatan kapal dengan menggunakan Finite Volume Method (FVM). Persamaan RANS (Reynolds- Averaged Navier-Stokes) dengan model turbulensi k-ε untuk memprediksi aliran turbulen dan Volume of Fluid (VOF) untuk mempresentasikan aliran 2 fasa. Pada penelitian ini digunakan metode overset mesh untuk memprediksi hambatan kapal agar mendapatkan akurasi yang baik. Hasil simulasi hambatan menunjukkan trend yang baik. Pada kecepatan tinggi, prediksi hambatan tidak memiliki hasil yang baik. Solusi yang ditawarkan pada Numerical ventilation problem (NVP) adalah dengan menggunakan metode phase replacement.Kata kunci: CFD, planing hull, RANS, overset mesh, NVP ABSTRACTThe prediction of planing hull resistance is more complicated than the displacement hull. It is caused by the more dominant hydrodynamic force at the bottom of the ship. The planing hull resistance characteristics are strongly influenced by trim and heave movements. In addition, the shape of the hullform also affects the ship's resistance, such as dead-rise angle, chine, strip, stephull, and others. The solution to predict ship resistance is by using the Finite Volume Method (FVM). RANS (Reynolds-Averaged Navier-Stokes) equation k-ε turbulence model was used to predict turbulent flow and Volume of Fluid (VOF) to present 2 phase flow. In this study, the overset mesh method was used to predict ship resistance in order to get good accuracy. Resistance simulation results showed a good trend. At high speeds, the prediction of resistance did not have good results. The solution offered in the Numerical ventilation problem (NVP) was to use the phase replacement method.Keywords: CFD, planing hull, RANS, overset mesh, NVP

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