scholarly journals Fan–Intake Interaction Under High Incidence

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Teng Cao ◽  
Nagabhushana Rao Vadlamani ◽  
Paul G. Tucker ◽  
Angus R. Smith ◽  
Michal Slaby ◽  
...  
Keyword(s):  
Numerical Study ◽  
Angle Of Incidence ◽  
Inlet Distortion ◽  
Distortion Level ◽  
3D Geometry ◽  
High Incidence ◽  
Mach Number Distribution ◽  
Unsteady Rans ◽  
Bypass Ratio ◽  
Insight Into

In this paper, we present an extensive numerical study on the interaction between the downstream fan and the flow separating over an intake under high incidence. The objectives of this investigation are twofold: (a) to gain qualitative insight into the mechanism of fan–intake interaction and (b) to quantitatively examine the effect of the proximity of the fan on the inlet distortion. The fan proximity is altered using the key design parameter, L/D, where D is the diameter of the intake, and L is the distance of the fan from the intake lip. Both steady and unsteady Reynolds-averaged numerical simulations (RANS) were carried out. For the steady calculations, a low-order fan model has been used, while a full 3D geometry has been used for the unsteady RANS. The numerical methodology is also thoroughly validated against the measurements for the intake-only and fan-only configurations on a high bypass ratio turbofan intake and fan, respectively. To systematically study the effect of fan on the intake separation and explore the design criteria, a simplified intake–fan configuration has been considered. In this fan–intake model, the proximity of the fan to the intake separation (L/D) can be conveniently altered without affecting other parameters. The key results indicate that, depending on L/D, the fan has either suppressed the level of the postseparation distortion or increased the separation-free operating range. At the lowest L/D (∼0.17), around a 5 deg increase in the separation-free angle of incidence was achieved. This delay in the separation-free angle of incidence decreased with increasing L/D. At the largest L/D (∼0.44), the fan was effective in suppressing the postseparation distortion rather than entirely eliminating the separation. Isentropic Mach number distribution over the intake lip for different L/D's revealed that the fan accelerates the flow near the casing upstream of the fan face, thereby decreasing the distortion level in the immediate vicinity. However, this acceleration effect decayed rapidly with increasing upstream distance from the fan-face.

scholarly journals Fan-Intake Interaction Under High Incidence

2016 ◽  
Author(s):  
Teng Cao ◽  
Nagabhushana Rao Vadlamani ◽  
Paul G. Tucker ◽  
Angus R. Smith ◽  
Michal Slaby ◽  
...  
Keyword(s):  
Numerical Study ◽  
Design Parameters ◽  
Angle Of Incidence ◽  
Flow Distortion ◽  
Distortion Level ◽  
3D Geometry ◽  
High Incidence ◽  
Unsteady Rans ◽  
Bypass Ratio ◽  
Insight Into

In this paper, we present an extensive numerical study on the interaction between the downstream fan and the flow separating over an intake under high incidence. The objectives of this investigation are twofold: (a) to gain qualitative insight into the mechanism of fan-intake interaction and (b) to quantitatively examine the sensitivity of the flow distortion (in terms of distortion coefficient DC60), to the key design parameters of the intake (Length, L / Diameter, D). Both steady and unsteady Reynolds Averaged Numerical Simulations (RANS) were carried out. For the steady calculations, a low order fan model has been used while a full 3D geometry has been used for the unsteady RANS. The numerical methodology is also thoroughly validated against the measurements for the intake-only and fan-only configurations on a high bypass ratio turbofan intake and fan respectively. To systematically study the effect of fan on the intake separation and explore the design criteria, a simplified intake-fan configuration has been considered. In this fan-intake model, the ratio of the intake length to diameter (L/D) can be conveniently altered without affecting other parameters. The key results indicate that, depending on L/D, the fan has either suppressed the level of the post separation distortion or increased the separation-free operating range. At the lowest L/D (∼ 0.17), around a 5° increase in the separation-free angle of incidence was achieved. This delay in the separation-free angle of incidence decreased with increasing L/D. At the largest L/D (∼ 0.44), the fan was effective in suppressing the post-separation distortion rather than entirely eliminating the separation. Isentropic Mach number distributions over the intake lip for different L/D’s revealed that the fan accelerates the flow upstream of the fan face, thereby decreasing the distortion level in the immediate vicinity. However, this acceleration effect decayed rapidly with increasing upstream distance from the fan-face.

scholarly journals Atmospheric radiation boundary conditions for the Helmholtz equation

2018 ◽  
Vol 52 (3) ◽  
pp. 945-964 ◽  
Author(s):  
Hélène Barucq ◽  
Juliette Chabassier ◽  
Marc Duruflé ◽  
Laurent Gizon ◽  
Michael Leguèbe
Keyword(s):  
Boundary Conditions ◽  
Helmholtz Equation ◽  
Acoustic Waves ◽  
Numerical Study ◽  
Outgoing Wave ◽  
Atmospheric Radiation ◽  
Angle Of Incidence ◽  
Radiation Boundary Conditions ◽  
Radiation Boundary ◽  
Dirichlet To Neumann Map

This work offers some contributions to the numerical study of acoustic waves propagating in the Sun and its atmosphere. The main goal is to provide boundary conditions for outgoing waves in the solar atmosphere where it is assumed that the sound speed is constant and the density decays exponentially with radius. Outgoing waves are governed by a Dirichlet-to-Neumann map which is obtained from the factorization of the Helmholtz equation expressed in spherical coordinates. For the purpose of extending the outgoing wave equation to axisymmetric or 3D cases, different approximations are implemented by using the frequency and/or the angle of incidence as parameters of interest. This results in boundary conditions called atmospheric radiation boundary conditions (ARBC) which are tested in ideal and realistic configurations. These ARBCs deliver accurate results and reduce the computational burden by a factor of two in helioseismology applications.

Active control of fan noise from high-bypass ratio aeroengines: a numerical study

2001 ◽  
Vol 105 (1053) ◽  
pp. 627-631
Author(s):  
P. Traub ◽  
F. Kennepohl ◽  
K. Heinig
Keyword(s):  
Active Control ◽  
Numerical Study ◽  
Active Noise Control ◽  
Sound Field ◽  
Primary Objective ◽  
Scale Model ◽  
Research Centre ◽  
Infinite Length ◽  
Circular Duct ◽  
Bypass Ratio

Abstract Under the national research project, dubbed Turbotech II, in which MTU Aero Engines, DLR Institute of Propulsion Technology and EADS Corporate Research Centre participate, active noise control (ANC) has been tested with a scale model fan of one metre diameter for a high bypass ratio aeroengine. MTU’s task in this project was to develop a computer code to predict the sound field in the intake duct of the fan-rig by the use of active control. The primary objective of the numerical study was to specify numbers of actuators (loudspeakers) and error sensors (microphones) and their positioning to control the harmonic sound power, radiated upstream to the duct intake. The computer model is based on the geometry of an annular or circular duct of rigid walls and infinite length, containing a subsonic axial uniform flow. The modal amplitudes of the primary sound field are input data. The actuators are modelled by acoustic monopoles. Two control algorithms have been used for achieving the control objective. The first consists simply in the reduction of the in-duct mean squared pressures. The second, so called modal control, is designed to cancel dominant modes selectively. Numerical results are presented using a typical configuration of wall mounted actuators and error sensors in the form of a number of rings uniformly distributed along the length of the intake duct. Guidelines have also been derived to design a favourable configuration of actuators and sensors. The findings of the numerical study are compared with the results of the ANC tests.

scholarly journals Method for fast determination of the angle of ionizing radiation incidence from data measured by a Timepix3 detector

2021 ◽  
Vol 10 (1) ◽  
pp. 63-70
Author(s):  
Felix Lehner ◽  
Jürgen Roth ◽  
Oliver Hupe ◽  
Marc Kassubeck ◽  
Benedikt Bergmann ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Incidence Angle ◽  
Computation Time ◽  
Incident Radiation ◽  
Angle Of Incidence ◽  
Time Behavior ◽  
Calculation Algorithm ◽  
3D Geometry ◽  
Photon Event ◽  
Radiation Incidence

Abstract. This paper presents a method of how to determine spatial angles of ionizing radiation incidence quickly, using a Timepix3 detector. This work focuses on the dosimetric applications where detectors and measured quantities show significant angle dependencies. A determined angle of incidence can be used to correct for the angle dependence of a planar Timepix3 detector. Up until now, only passive dosemeters have been able to provide a correct dose and preserve the corresponding incidence angle of the radiation. Unfortunately, passive dosemeters cannot provide this information in “real” time. In our special setup we were able to retrieve the spatial angles with a runtime of less than 600 ms. Employing the new Timepix3 detector enables the use of effective data analysis where the direction of incident radiation is computed from a simple photon event map. In order to obtain this angle, we combine the information extracted from the map with known 3D geometry surrounding the detector. Moreover, we analyze the computation time behavior, conditions and optimizations of the developed spatial angle calculation algorithm.

scholarly journals A Mixed-Fidelity Numerical Study for Fan–Distortion Interaction

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Yunfei Ma ◽  
Jiahuan Cui ◽  
Nagabhushana Rao Vadlamani ◽  
Paul Tucker
Keyword(s):  
Immersed Boundary Method ◽  
Numerical Study ◽  
Immersed Boundary ◽  
Fan Performance ◽  
Inlet Distortion ◽  
Eddy Simulation ◽  
Pressure Distributions ◽  
Large Eddy ◽  
Dynamics Method ◽  
Good Agreement

Inlet distortion often occurs under off-design conditions when a flow separates within an intake and this unsteady phenomenon can seriously impact fan performance. Fan–distortion interaction is a highly unsteady aerodynamic process into which high-fidelity simulations can provide detailed insights. However, due to limitations on the computational resource, the use of an eddy resolving method for a fully resolved fan calculation is currently infeasible within industry. To solve this problem, a mixed-fidelity computational fluid dynamics method is proposed. This method uses the large Eddy simulation (LES) approach to resolve the turbulence associated with separation and the immersed boundary method (IBM) with smeared geometry (IBMSG) to model the fan. The method is validated by providing comparisons against the experiment on the Darmstadt Rotor, which shows a good agreement in terms of total pressure distributions. A detailed investigation is then conducted for a subsonic rotor with an annular beam-generating inlet distortion. A number of studies are performed in order to investigate the fan's influence on the distortions. A comparison to the case without a fan shows that the fan has a significant effect in reducing distortions. Three fan locations are examined which reveal that the fan nearer to the inlet tends to have a higher pressure recovery. Three beams with different heights are also tested to generate various degrees of distortion. The results indicate that the fan can suppress the distortions and that the recovery effect is proportional to the degree of inlet distortion.

Abstract WP82: Transcranial Doppler Detection of Microembolic Signals During the Advancement and Deployment of Pipeline Embolization Devices in Unruptured Intracranial Aneurysm Repair

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Andres Hughes ◽  
Mark J Dannenbaum ◽  
Peng R Chen ◽  
Arthur L Day ◽  
Huimahn A Choi ◽  
...  
Keyword(s):  
Transcranial Doppler ◽  
Neurological Complication ◽  
Initial Study ◽  
Relative Safety ◽  
High Incidence ◽  
Device Placement ◽  
The Mean ◽  
Aneurysm Repair ◽  
Very High ◽  
Insight Into

Introduction: Pipeline embolization devices (PED) have become an essential tool in the endovascular treatment of complex intracranial aneurysms. A high-density stent like device, the PED functions to redirect blood flow and facilitate the growth and remodeling of the artery. Postoperative ischemic stroke proves to be the most common neurological complication associated with treatment, ranging from about 3-6% with most occurring within 30 days. Transcranial Doppler (TCD) monitoring has been used in the past to evaluate similar procedures by measuring the occurrence of microembolic signals (MES). Due to the delivery and manipulation of the PED and its thrombotic nature, microembolic events have been postulated to form during device placement and contribute to thromboembolism. Our initial study is the first to detect and measure MES during a PED procedure. Methods: Patients undergoing endovascular PED treatment were simultaneously monitored with TCD. MES were detected, separated from artifacts, and counted for each step. Results: Embolic signals were detected in all patients and were highest during deployment. With 3 PED deployments in the paraophthalmic ICA of 2 patients, the mean MES during PED deployment was 515 +/- 46. Average emboli per second during deployment was 1.62 +/- 0.59 verses 0.30 +/- 0.12 emboli per second observed prior to microcatheter insertion and manipulation. Conclusion: A very high incidence of MES was observed during the procedure and PED deployment. The little success thus far in elucidating a possible mechanism to account for PED’s associated complications warrants more investigation. Determining the occurrence of MES might reveal insight into the relative safety of each step and on the formation of distal thromboembolisms.

A 2.5D numerical study on open water hydrodynamic performance of a Voith-Schneider propeller

2019 ◽  
Vol 20 (6) ◽  
pp. 617
Author(s):  
Mohammad Bakhtiari ◽  
Hassan Ghassemi
Keyword(s):  
Numerical Method ◽  
Thrust Force ◽  
Numerical Study ◽  
Open Water ◽  
Hydrodynamic Performance ◽  
Maximum Efficiency ◽  
Water Efficiency ◽  
Blade Thickness ◽  
Unsteady Rans ◽  
Marine Vessels

Marine cycloidal propeller (MCP) is a special type of marine propulsors that provides high maneuverability for marine vessels. In a MCP, the propeller axis of rotation is perpendicular to the direction of thrust force. It consists of a number of lifting blade. Each blade rotates about the propeller axis and simultaneously pitches about its own axis. The magnitude and direction of thrust force can be adjusted by controlling the propeller pitch. Voith-Schneider propeller (VSP) is a low-pitch MCP with pure cycloidal blade motion allowing fast, accurate, and stepless control of thrust magnitude and direction. Generally, low-pitch cycloidal propellers are used in applications with low speed maneuvering requirements, such as tugboats, minesweepers, etc. In this study, a 2.5D numerical method based on unsteady RANS equations with SST k-ω turbulent model was implemented to predict the open water hydrodynamic performance of a VSP for different propeller pitches and blade thicknesses. The numerical method was validated against the experimental data before applying to VSP. The results showed that maximum open water efficiency of a VSP is enhanced by increasing the propeller pitch. Furthermore, the effect of blade thickness on open water efficiency is different at various advance coefficients, so that the maximum efficiency produced by the VSP decreases with increasing blade thickness at different propeller pitches.

IMPULSIVELY STARTED FLOW TOPOLOGY AROUND TANDEM ARRANGEMENT OF TWO SQUARE CYLINDER AT INCIDENCE

2012 ◽  
Vol 19 ◽  
pp. 100-108
Author(s):  
SUNIL MANOHAR DASH ◽  
THONG-SEE LEE
Keyword(s):  
Numerical Study ◽  
Flow Direction ◽  
Main Stream ◽  
Angle Of Incidence ◽  
Flow Topology ◽  
Pressure Distributions ◽  
Square Prism ◽  
Tandem Square Cylinders ◽  
Type 3

Numerical study of impulsively started flow over two tandem square cylinders where former cylinder is rotated at angles (0-45deg) to main stream flow direction keeping later one inline to flow stream with a separation of twice the side length of square prism between the centers of cylinders is performed using FVM code solver FLUENT 6.3.26. Temporal developments of streamlines around cylinders are studied for laminar flow regime ( Re = 100). Flow pattern formed are categories into Type-1, Type-2, Type-3 & Type-4 as per vortices growth at corresponding angle of incidence which are novel results of present study. Pressure distributions over the surface of cylinders are also monitored.

scholarly journals On Efficient Estimation of Process Variability

Symmetry ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 554
Author(s):  
Tanveer Akhlaq ◽  
Muhammad Ismail ◽  
Muhammad Qaiser Shahbaz
Keyword(s):  
Numerical Study ◽  
Empirical Studies ◽  
Efficient Estimation ◽  
Process Variability ◽  
Good Insight ◽  
Exponential Method ◽  
Process Dispersion ◽  
The Mean ◽  
Insight Into ◽  
Better Than

Variability or dispersion plays an important role in any process and provides insight into the spread of data from some central point, usually the mean. A process with less spread is preferred over a process in which values differ greatly from the mean. Various methods are available to estimate the process dispersion by using information on the variable of interest. Certain additional variables provide good insight to estimate the process dispersion. In this paper, we propose an efficient method for the estimation of process variability by using the exponential method. The properties of the proposed method were studied. We conducted simulation and empirical studies to compare the proposed method with some existing methods of estimation of variability. The results of the numerical study show that our proposed method is better than the other methods used in the study.

The Plane Parallel Flow of a Binary Mixture of Fluids

1981 ◽  
Vol 48 (4) ◽  
pp. 707-716
Author(s):  
L. M. Srivastava ◽  
V. P. Srivastava
Keyword(s):  
Binary Mixture ◽  
Particle Deposition ◽  
Numerical Study ◽  
Infinite Plate ◽  
Small Diameter ◽  
Hankel Transform ◽  
Physical Importance ◽  
Strong Motivation ◽  
Insight Into ◽  
Made In

The flow of a binary mixture of chemically inert incompressible, Newtonian fluids over an infinite plate, set into motion in its plane by impulse and by oscillation, is studied. The binary mixture consists of (i) two different viscous density nonstratified fluids, and (ii) two different viscous density stratified fluids. The exact solutions are obtained using two methods, (i) Laplace transform and (ii) Hankel transform. To further study the velocities and the wall shear stress, asymptotic expansion are found for small and large times. Some other results of physical importance such as results for noninteracting fluids, strongly interacting fluids, and extremely different fluids are also derived and compared analytically with other results. Finally, to gain an insight into the patterns of the flow, numerical study of the results has been made in detail using digital computer. A strong motivation of the present analysis has been the hope that such a theory of fluids is useful in providing some insight in rheological properties of complex fluids as polymers, liquid crystals and, in particular, blood in the vessels of small diameter. Also the theory of fluids might provide an improved understanding of such diverse subjects as diffusion of proteins, swimming of micro-organism and particle deposition in respiratory tract.

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