Unsteady Euler analysis of the flowfield of a propfan at an angle of attack
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Nallasamy, M.↗
Engineering topics
Groeneweg, J. F.
Publications and source records attributed to Groeneweg, J. F..
Unsteady blade-surface pressures on a large-scale advanced propeller - Prediction and data
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Nallasamy, M.↗
Unsteady flowfield of a propfan at takeoff conditions
The unsteady flowfield of a propfan operation at takeoff conditions with angular inflow is examined by solving the three-dimensional Euler equations. The operating conditions considered are: Mach no. = 0.31, advance ratio = 1.6, and inflow angle to the propfan = 8.3 deg. The predicted results clearly show the cyclic variations of the blade power and thrust coefficients due to angular inflow. The flow changes from blade passage to passage are illustrated in terms of static pressure contours. The predicted blade surface pressure waveforms were compared with flight measurements. The predictions at the inboard radial station, r/R = 0.68, show reasonable agreement with flight data. At the outboard radial station, r/R = 0.95, where the interactions of the tip vortex, the tip-region flow and the blade wake appear to result in a complex nonlinear measured response. The prediction shows poor agreement.
Nallasamy, M.↗
Near-field noise of a single-rotation propfan at an angle of attack
The near field noise characteristics of a propfan operating at an angle of attack are examined utilizing the unsteady pressure field obtained from a 3-D Euler simulation of the propfan flowfield. The near field noise is calculated employing three different procedures: a direct computation method in which the noise field is extracted directly from the Euler solution, and two acoustic-analogy-based frequency domain methods which utilize the computed unsteady pressure distribution on the propfan blades as the source term. The inflow angles considered are -0.4, 1.6, and 4.6 degrees. The results of the direct computation method and one of the frequency domain methods show qualitative agreement with measurements. They show that an increase in the inflow angle is accompanied by an increase in the sound pressure level at the outboard wing boom locations and a decrease in the sound pressure level at the (inboard) fuselage locations. The trends in the computed azimuthal directivities of the noise field also conform to the measured and expected results.
Nallasamy, M.↗
Near-field noise of a single rotation propfan at an angle of attack
The near-field noise characteristics of a propfan operating at an angle of attack are examined utilizing the unsteady pressure field obtained from a three-dimensional Euler simulation of the propfan flowfield. The near-field noise is calculated employing three different procedures: a direct computation method in which the noise field is extracted directly from the Euler solution, and two acoustic-analogy-based frequency domain methods which utilize the computed unsteady pressure distribution on the propfan blades as the source term. The inflow angles considered are -0.4, 1.6, and 4.6 degrees. The results of the direct computation method and one of the frequency domain methods show qualitative agreement with measurements. They show that an increase in the inflow angle is accompanied by an increase in the sound pressure level at the outboard wing boom locations and a decrease in the sound pressure level at the (inboard) fuselage locations. The trends in the computed azimuthal directivities of the noise field also conform to the measured and expected results.
Nallasamy, M.↗
Prediction of unsteady blade surface pressures on an advanced propeller at an angle of attack
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Nallasamy, M.↗
Unsteady blade surface pressures on a large-scale advanced propeller - Prediction and data
An unsteady three dimensional Euler analysis technique is employed to compute the flowfield of an advanced propeller operating at an angle of attack. The predicted blade pressure waveforms are compared with wind tunnel data at two Mach numbers, 0.5 and 0.2. The inflow angle is three degrees. For an inflow Mach number of 0.5, the predicted pressure response is in fair agreement with data: the predicted phases of the waveforms are in close agreement with data while the magnitudes are underpredicted. At the low Mach number of 0.2 (take-off) the numerical solution shows the formation of a leading edge vortex which is in qualitative agreement with measurements. However, the highly nonlinear pressure response measured on the blade suction surface is not captured in the present inviscid analysis.
Nallasamy, M.↗
Unsteady blade-surface pressures on a large-scale advanced propeller: Prediction and data
An unsteady 3-D Euler analysis technique is employed to compute the flow field of an advanced propeller operating at an angle of attack. The predicted blade pressure waveforms are compared with wind tunnel data at two Mach numbers, 0.5 and 0.2. The inflow angle is three degrees. For an inflow Mach number of 0.5, the predicted pressure response is in fair agreement with data: the predicted phases of the waveforms are in close agreement with data while the magnitudes are underpredicted. At the low Mach number of 0.2 (takeoff), the numerical solution shows the formation of a leading edge vortex which is in qualitative agreement with measurements. However, the highly nonlinear pressure response measured on the blade suction surface is not captured in the present inviscid analysis.
Nallasamy, M.↗
Unsteady Euler analysis of the flow field of a propfan at an angle of attack
The effects of angle of attack of a propfan on the blade loading and details of the flow field by solving the unsteady three-dimensional Euler equations are examined. The configuration considered is the SR7L propeller at cruise condition and the inflow angles considered are 4.6 degrees, 1.6 degrees and -0.4 degrees. The results indicate that the blade response is nearly sinusoidal at low inflow angles (1.6 degrees and -0.4 degrees) and significant deviations from sinusoidal behavior occur at an inflow angle of 4.6 degrees due to the presence of strong shocks on both suction and pressure surfaces of the blade. The detailed flow in the blade passages shows that a shock formed on the suction surface during the highly loaded portion of the revolution extends across the passage to the pressure surface. An increase in inflow angle results in an increase in blade loading on the down-going side and a decrease in loading on the up-going side.
Nallasamy, M.↗
Unsteady Euler analysis of the flowfield of a propfan at an angle of attack
The paper examines the effects of angle of attack of a propfan on the blade loading and details of the flowfield by solving the unsteady three-dimensional Euler equations. The configuration considered is the SR7L propeller at cruise condition and the inflow angles considered are 4.6, 1.6 and -0.4 deg. The results indicate that the blade response is nearly sinusoidal at low inflow angles (1.6 and -0.4 deg) and significant deviations from sinusoidal behavior occur at an inflow angle of 4.6 deg due to the presence of strong shocks on both suction and pressure surfaces of the blade. The detailed flow in the blade passages shows that a shock formed on the suction surface during the highly loaded portion of the revolution extends across the passage to the pressure surface. An increase in inflow angle results in an increase in blade loading on the down-going side and a decrease in loading on the up-going side.
Nallasamy, M.↗
Prediction of Unsteady Blade Surface Pressures on an Advanced Propeller at an Angle of Attack
The numerical solution of the unsteady, three-dimensional, Euler equations is considered in order to obtain the blade surface pressures of an advanced propeller at an angle of attack. The specific configuration considered is the SR7L propeller at cruise conditions with a 4.6 deg inflow angle corresponding to the plus 2 deg nacelle tilt of the Propeller Test Assessment (PTA) flight test condition. The results indicate nearly sinusoidal response of the blade loading, with angle of attack. For the first time, detailed variations of the chordwise loading as a function of azimuthal angle are presented. It is observed that the blade is lightly loaded for part of the revolution and shocks appear from hub to about 80 percent radial station for the highly loaded portion of the revolution.
Nallasamy, M.↗
High-speed propeller performance and noise predictions at takeoff/landing conditions
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Nallasamy, M.↗
Prediction of unsteady blade surface pressures on an advanced propeller at an angle of attack
The paper considers the numerical solution of the unsteady, three-dimensional, Euler equations to obtain the blade surface pressures of an advanced propeller at an angle of attack. The specific configuration considered is the SR7L propeller at cruise conditions with a 4.6 deg inflow angle corresponding to the +2 deg nacelle tilt of the Propeller Test Assessment (PTA) flight test condition. The results indicate nearly sinusoidal response of the blade loading, with angle of attack. For the first time, detailed variations of the chordwise loading as a function of azimuthal angle are presented. It is observed that the blade is lightly loaded for part of the revolution and shocks appear from hub to about 80 percent radial station for the highly loaded portion of the revolution.
Nallasamy, M.↗
High-speed propeller noise predictions - Effects of boundary conditions used in blade loading calculations
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Nallasamy, M.↗
High speed propeller performance and noise predictions at takeoff/landing conditions
The performance and noise of a high speed SR-7A model propeller under takeoff/landing conditions are considered. The blade loading distributions are obtained by solving the three-dimensional Euler equations and the sound pressure levels are computed using a time domain approach. At the nominal takeoff operating point, the blade sections near the hub are lightly or negatively loaded. The chordwise loading distributions are distinctly different from those of cruise conditions. The noise of the SR-7A model propeller at takeoff is dominated by the loading noise, similar to that at cruise conditions. The waveforms of the acoustic pressure signature are nearly sinusoidal in the plane of the propeller. The computed directivity of the blade passing frequency tone agrees fairly well with the data at nominal takeoff blade angle.
Nallasamy, M.↗
Euler analysis of the three-dimensional flow field of a high-speed propeller - Boundary condition effects
The results of an investigation of the effects of far field boundary conditions on the solution of the three dimensional Euler equations governing the flow field of a high speed single rotation propeller are presented. The results show that the solutions obtained with the nonreflecting boundary conditions are in good agreement with experimental data. The specification of nonreflecting boundary conditions is effective in reducing the dependence of the solution on the location of the far field boundary. Details of the flow field within the blade passage and the tip vortex are presented. The dependence of the computed power coefficient on the blade passage and the tip vortex are presented. The dependence of the computed power coefficient on the blade setting angle is examined.
Nallasamy, M.↗
High-speed propeller noise predictions: Effects of boundary conditions used in blade loading calculations
The acoustics of an advanced single rotation SR-3 propeller at cruise conditions are studied employing a time-domain approach. The study evaluates the acoustic significance of the differences in blade pressures computed using nonreflecting rather than hard wall boundary conditions in the three-dimensional Euler code solution. The directivities of the harmonics of the blade passing frequency tone and the effects of chordwise loading on tone directivity are examined. The results show that the maximum difference in the computed sound pressure levels due to the use of blade pressure distributions obtained with the nonreflecting rather than the hard wall boundary conditions is about 1.5 dB. The blade passing frequency tone directivity obtained in the present study shows good agreement with jetstar flight data.
Nallasamy, M.↗
Euler analysis of the three dimensional flow field of a high-speed propeller: Boundary condition effects
The results of an investigation of the effects of far field boundary conditions on the solution of the three dimensional Euler equations governing the flow field of a high speed single rotation propeller are presented. The results show that the solutions obtained with the nonreflecting boundary conditions are in good agreement with experimental data. The specification of nonreflecting boundary conditions is effective in reducing the dependence of the solution on the location of the far field boundary. Details of the flow field within the blade passage and the tip vortex are presented. The dependence of the computed power coefficient on the blade passage and the tip vortex are presented. The dependence of the computed power coefficient on the blade setting angle is examined.
Nallasamy, M.↗