A Comparison of Propeller Wake Models for Distributed Electric Propulsion and eVTOL Aircraft in Complex Flow Conditions

2022 ◽  
Author(s):  
Racheal M. Erhard ◽  
Juan J. Alonso
Keyword(s):  
Electric Propulsion ◽  
Flow Conditions ◽  
Complex Flow ◽  
Propeller Wake

Total Pressure Correction of a Sub-Miniature Five-Hole Probe in Areas of Pressure Gradients

2012 ◽  
Author(s):  
J. Town ◽  
A. Akturk ◽  
C. Camcı
Keyword(s):  
Pressure Measurement ◽  
Measurement Errors ◽  
Total Pressure ◽  
Pressure Gradients ◽  
Pressure Data ◽  
Flow Conditions ◽  
Complex Flow ◽  
Ducted Fan ◽  
The Difference ◽  
Best Fit

Five-hole probes, being a dependable and accurate aerodynamic tools, are excellent choices for measuring complex flow fields. However, total pressure gradients can induce measurement errors. The combined effect of the different flow conditions on the ports causes the measured total pressure to be prone to a greater error. This paper proposes a way to correct the total pressure measurement. The correction is based on the difference between the measured total pressure data of a Kiel probe and a sub-miniature prism-type five-hole probe. By comparing them in a ducted fan related flow field, a line of best fit was constructed. The line of best fit is dependent on the slope of the line in a total pressure versus span and difference in total pressure between the probes at the same location. A computer program, performs the comparison and creates the correction equation. The equation is subsequently applied to the five-hole probe total pressure measurement, and the other dependent values are adjusted. The validity of the correction is then tested by placing the Kiel probe and the five-hole probe in ducted fans with a variety of different tip clearances.

The scaling of mineral dissolution rates under complex flow conditions

2020 ◽  
Vol 274 ◽  
pp. 63-78 ◽  
Author(s):  
Rong Li ◽  
Chen Yang ◽  
Dongfang Ke ◽  
Chongxuan Liu
Keyword(s):  
Mineral Dissolution ◽  
Flow Conditions ◽  
Complex Flow ◽  
Dissolution Rates

URANS Simulation of an Appended Hull During Steady Turn With Propeller Represented by an Actuator Disk Model

2011 ◽  
Author(s):  
Charles M. Dai ◽  
Ronald W. Miller
Keyword(s):  
Flow Field ◽  
Cross Flow ◽  
Field Measurements ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Complex Flow ◽  
Ship Maneuvering ◽  
Disk Model ◽  
Actuator Disk ◽  
Propeller Wake

This paper reports on the comparison between computational simulations and experimental measurements of a surface vessel in steady turning conditions. The primary purpose of these efforts is to support the development of physics-based high fidelity maneuvering simulation tools by providing accurate and reliable hydrodynamic data with relevance to maneuvering performances. Reynolds Averaged Unsteady Navier Stokes Solver (URANS): CFDSHIPIOWA was used to perform simulations for validation purposes and for better understanding of the fundamental flow physics of a hull under maneuvering conditions. The Propeller effects were simulated using the actuator disk model included in CFDShip-Iowa. The actuator disk model prescribes a circumferential averaged body force with axial and tangential components. No propeller generated side forces are accounted for in the model. This paper examines the effects of actuator disk model on the overall fidelity of a RANS based ship maneuvering simulations. Both experiments and simulations provide physical insights into the complex flow interactions between the hull and various appendages, the rudders and the propellers. The experimental effort consists of flow field measurements using Stereo Particle-Image Velocimetry (SPIV) in the stern region of the model and force and moment measurements on the whole ship and on ship components such as the bilge keels, the rudders, and the propellers. Comparisons between simulations and experimental measurements were made for velocity distributions at different transverse planes along the ship axis and different forces components for hull, appendages and rudders. The actuator disk model does not predict any propeller generated side forces in the code and they need to be taken into account when comparing hull and appendages generated side forces in the simulations. The simulations were compared with experimental results and they both demonstrate the cross flow effect on the transverse forces and the propeller slip streams generated by the propellers during steady turning conditions. The hull forces (include hull, bilge keels, skeg, shafting and strut) predictions were better for large turning circle case as compared with smaller turning circle. Despite flow field simulations appear to capture gross flow features qualitatively; detailed examinations of flow distributions reveal discrepancies in predictions of propeller wake locations and secondary flow structures. The qualitative comparisons for the rudders forces also reveal large discrepancies and it was shown that the primary cause of discrepancies is due to poor predictions of velocity inflow at the rudder plane.

scholarly journals A CFD Study on Two-Phase Frozen Flow of Air/Water Through a Safety Relief Valve

2015 ◽  
Vol 13 (4) ◽  
pp. 533-540 ◽  
Author(s):  
Moftah Alshaikh ◽  
William Dempster
Keyword(s):  
Fluid Model ◽  
Critical Mass ◽  
Velocity Slip ◽  
Flow Conditions ◽  
Complex Flow ◽  
Relief Valve ◽  
Two Phase ◽  
Mass Flows ◽  
Two Fluid Model ◽  
Two Fluid

Abstract The air-water two phase critical flows through a safety relief valve commonly used in the refrigeration industry is examined with particular emphasis on the prediction of the critical mass flowrates using CFD based approaches. The expansion of the gas through the valve and the associated acceleration is coupled to the liquid phase and results in changes to the velocity slip with the possibility of influencing the choking conditions and the magnitude of the critical mass flows. These conditions are poorly reported in the literature for safety valves. This paper presents a study where the ability of established two phase multi-dimensional modelling approaches to predict such conditions are investigated. Comparison with the simplified mixture model will show that this model tends to underestimate mass flowrates for medium to high liquid mass fraction. However, the two fluid model can adequately account for the thermal and mechanical non equilibrium for these complex flow conditions with the use of simplified droplet sizing rules.

scholarly journals Tracer test modeling for local scale residence time distribution characterization in an artificial recharge site

2016 ◽  
Author(s):  
Cristina Valhondo ◽  
Lurdes Martínez-Landa ◽  
Jesús Carrera ◽  
Juan J. Hidalgo ◽  
Isabel Tubau ◽  
...  
Keyword(s):  
Water Quality ◽  
Artificial Recharge ◽  
Groundwater Resources ◽  
Homogeneous Model ◽  
Tracer Test ◽  
Flow Conditions ◽  
Transport Parameters ◽  
Complex Flow ◽  
Concentration Data ◽  
Heterogeneous Model

Abstract. Artificial recharge of aquifers is a technique for improving water quality and increasing groundwater resources. Understanding the fate of a potential contaminant requires knowledge of the residence times distribution (RTD) of the water beneath the artificial recharge infrastructure. A simple way to obtain the RTDs is to perform a tracer test. We performed a pulse injection tracer test in an artificial recharge system through an infiltration basin to obtain the breakthrough curves, which yield directly the RTDs. These were very broad and we used a numerical model to interpret them, and to extend the characterization to other flow conditions. The model comprised nine layers at the site scaled to emulate the layering of aquifer deposits. Two types of hypotheses were considered: homogeneous (all flow and transport parameters identical for every layer) and heterogeneous (diverse parameters for each layer). The parameters were calibrated against the head and concentration data in both model types, which were validated quite satisfactory against 1,1,2-Trichloroethane and electrical conductivity data collected over a long period of time with highly varying flow conditions. We found that the broad RTDs were caused by both the complex flow structure generated under the basin (the homogeneous model produced broad RTDs) and the heterogeneity of the media (the heterogeneous model yielded much better fits). We conclude that acknowledging heterogeneity is required to properly assess mixing and broad RTDs, which are required to explain the water quality improvement of artificial recharge basins.

Secondary Flow Structure Induced by Physiologically Relevant Waveform in a Curved Tube

2009 ◽  
Author(s):  
Chekema N. Prince ◽  
Sean D. Peterson ◽  
Michael W. Plesniak
Keyword(s):  
Secondary Flow ◽  
Blood Vessels ◽  
Complex Geometry ◽  
Vascular System ◽  
Flow Regimes ◽  
Flow Conditions ◽  
Complex Flow ◽  
Curved Tube ◽  
Secondary Flow Structure ◽  
The Impact

The complex geometry of the vascular system can induce the development of complex primary and secondary flow regimes within blood vessels. Recent literature has focused on the impact of these complex flow regimes on endothelial cells (EC), which line blood vessels, and their role on the progression of vascular disease. One such disease, atherosclerosis has been linked to the reaction of ECs to flow conditions. Atherosclerosis is often treated by stent implantation to return the vessel lumen to its native diameter. It is hypothesized that stent struts may alter the development of secondary flow within the vessel and cause re-stenosis and/or thrombosis distal to the stent.

An On-line Automatic Flow Measurement Method for an Open Channel under Complex Flow Conditions

2016 ◽  
Vol 9 (7) ◽  
pp. 353-364
Author(s):  
Tanghuai Fan ◽  
Jie Shen ◽  
Guofang Lv ◽  
Jiahua Zhang ◽  
Xijun Yan
Keyword(s):  
Flow Measurement ◽  
Measurement Method ◽  
Open Channel ◽  
Flow Conditions ◽  
Complex Flow ◽  
On Line

Experimental and Numerical Analysis of the Flow Structure and Dust Separation Inside a Pre-Swirl Cooling Air System

2003 ◽  
Author(s):  
O. Schneider ◽  
H. J. Dohmen ◽  
F.-K. Benra ◽  
D. Brillert
Keyword(s):  
Numerical Analysis ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Flow Conditions ◽  
Test Rig ◽  
Complex Flow ◽  
Air System ◽  
Cooling Air

Improvements in efficiency and performance of gas turbines require a better understanding of the internal cooling air system which provides the turbine blades with cooling air. With the increase of cooling air passing through the internal air system, a greater amount of air borne particles is transported to the film cooling holes at the turbine blade surface. In spite of their small size, these holes are critical for blockage. Blockage of only a few holes could have harmful effects on the cooling film surrounding the blade. As a result, a reduced mean time between maintenance or even unexpected operation faults of the gas turbine during operation could occur. Experience showed a complex interaction of cooling air under different flow conditions and its particle load. To get more familiar with all these influences and the system itself, a test rig has been built. With this test rig, the behavior of particles in the internal cooling air system can be studied at realistic flow conditions compared to a modern, heavy duty gas turbine. It is possible to simulate different particle sizes and dust concentrations in the coolant air. The test rig has been designed to give information about the quantity of separated particles at various critical areas of the internal air system [1]. The operation of the test rig as well as analysis of particles in such a complex flow system bear many problems, addressed in previous papers [1,2,3]. New theoretical studies give new and more accurate results, compared to the measurements. Furthermore the inspection of the test rig showed dust deposits at unexpected positions of the flow path, which will be discussed by numerical analysis.

Steady and Dynamic Models of Fuel and Air Flow in Carburetors for Small Engines

2005 ◽  
Vol 127 (4) ◽  
pp. 778-786 ◽  
Author(s):  
Diego A. Arias ◽  
Timothy A. Shedd
Keyword(s):  
Dynamic Models ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Small Diameter ◽  
Phase Flow ◽  
Flow Conditions ◽  
Dynamic Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Small Engines

This work presents the mathematical model of a complex flow network containing short metering orifices, compressible flow, and two-phase flow in small diameter pipes. It has been developed to study the steady and dynamic flows in a carburetor for small engines. It extends the previously published models by incorporating a detailed review of two-phase flow pressure drop, the effect of the fuel well on the control of air-bleed flow, and dynamic flow. The homogeneous two-phase flow model, which is commonly used in previous models, was compared to an empirical correlation derived from experiments in small pipes and found to be in poor agreement. In order to assess dynamic flow conditions, the model was extended by solving instantaneous one-dimensional Navier-Stokes equations in single-phase pipes. This strategy proved successful in explaining the mixture enrichment seen under pulsating flow conditions. The model was also used to derive a sensitivity analysis of geometries and physical properties of air and fuel.

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