## About

41

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Introduction

Matthew Ringuette currently works at the Department of Mechanical & Aerospace Engineering at the University at Buffalo, The State University of New York. His research interests are experimental fluid mechanics, vortex dynamics, unsteady aerodynamics, bio-inspired propulsion with applications to autonomous air and underwater vehicles, fluid-structure interactions, and high-speed flow.

## Publications

Publications (41)

Dynamic effects of wing planform changes are investigated with the goal of gust alleviation. Force measurements are done on a low-aspect-ratio high-angle-of-attack translating wing having a rectangular planform that incorporates a moving tip with in-plane rotation and sweep. To create streamwise gusts, the wing is towed in a water tank from constan...

Dynamic Mode Decomposition (DMD) yields a linear, approximate model of a system's dynamics that is built from data. We seek to reduce the order of this model by identifying a reduced set of modes that best fit the output. We adopt a model selection algorithm from statistics and machine learning known as Least Angle Regression (LARS). We modify LARS...

An analytical model is developed for the lift force produced by unsteady rotating wings; this configuration is a simple representation of a flapping wing. Modelling this is important for the aerodynamic and control-system design for bio-inspired drones. Such efforts have often been limited to being two-dimensional, semi-empirical, sometimes computa...

The NATO RTO AVT-202 task group was a collaborative effort to study the fundamental unsteady low Reynolds number aerodynamics of lift production in highly separated flows. Experimental and numerical results are presented here, compiled from four different research groups, to describe the evolution of the flow around a rotating wing experiencing uns...

We employ experiments to study aspect effects on the vortex structure, circulation and lift force for flat-plate wings rotating from rest at 45 angle of attack, which represents a simplified hovering-wing half-stroke. We use the time-varying, volumetric AR = 2 data of Carr et ol. (Exp. Fluids, vol. 54, 2013, pp. 1-26), reconstructed from phase-lock...

The development of a nonintrusive microwave shock-speed measurement for expansion tunnels is presented, based on microwave standing-wave reflection. Testing is performed in a large-scale expansion-tunnel facility, with the goal of characterizing viscous effects. Expansion tunnels generate high-enthalpy test conditions for short test times, and the...

The use of flow field information to compute the fluid dynamic force on a body is investigated with specific application to experimental volumetric measurements. The calculation method used avoids the explicit evaluation of the pressure on the boundaries. It is shown that errors in the data introduce an artificial dependence of the calculations on...

Efforts to develop bio-inspired micro air vehicles (MAV) have motivated flapping-wing aerodynamics research. A syringe pump delivers the mixture at a very low flow rate to a hypodermic tube, which is carefully positioned near the model manually, then removed lengthwise. Once ensuring the dye is stationary, the run is executed. Identifying injection...

Force measurements are conducted on a low-aspect-ratio (
) trapezoidal flat plate that rotates at 90° angle of attack and performs an advancing stroke from rest followed by a returning stroke. The parameters varied are the rotational amplitude of the motion and the rest time between the advancing and returning strokes. The unsteady normal forces tr...

We experimentally investigate the flow generated on the leeward face of a rotating trapezoidal flat plate of low-aspect-ratio; the motion is an advancing stroke from rest at 90° angle of attack with Reynolds numbers of O(103). The objectives are to characterize the fluid velocity near the tip of the plate for different plate kinematics. The experim...

We investigate experimentally the effect of aspect ratio (
) on the time-varying, three-dimensional flow structure of flat-plate wings rotating from rest at 45° angle of attack. Plates of
= 2 and 4 are tested in a 50 % by mass glycerin–water mixture, with a total rotation of ϕ = 120° and a matched tip Reynolds number of 5,000. The time-varying,...

We investigate experimentally the effect of aspect ratio (AR) on the leading-edge vortex (LEV) circulation and lift force for flat-plate wings rotating from rest at 45° angle of attack. The objectives are to understand the influence of AR on the variation of LEV circulation with span and its scaling with kinematics, the tip vortex (TV) formation an...

We investigate experimentally the unsteady, three-dimensional flow structure and forces of rotating, at-plate wings starting from rest, focusing on aspect ratio (A) effects. The wings are rectangular with AR = 2 and 4 at 45° angle of attack, the velocity program is trapezoidal with a total rotation of 120°, and the tip Reynolds number is matched at...

We investigate experimentally the effect of aspect ratio (AR) on the unsteady, three-dimensional vortex structure of low-AR, flat-plate wings rotating from rest with a 45° angle of attack. This configuration is a simplified model of a flapping-wing hovering half-stroke. The objectives are to quantitatively characterize the evolution of the detailed...

We investigate experimentally the unsteady, three-dimensional vortex formation of low-aspect-ratio, trapezoidal flat-plate fins undergoing rotation from rest at a 90° angle of attack and Reynolds numbers of O(103). The objectives are to characterize the unsteady three-dimensional vortex structure, examine vortex saturation, and understand the effec...

We investigate experimentally the unsteady, three-dimensional vortex formation of lowaspect-ratio flat plates undergoing rotation from rest at fixed angles of attack and low Reynolds number (order 10 3 ). Two configurations are investigated: a trapezoidal plate at 90° angle of attack that is a simplified model of a fish-fin starting flow, and recta...

We investigate vortex saturation for a flat plate wing that simultaneously rotates and pitches. A vortex is saturated when it attains maximum circulation, which may occur at a non-dimensional time called the formation number. The experiment is done in a water tank and flow visualization is used to obtain the three-dimensional flow structure. We exa...

We investigate the unsteady flow of fish fin-like plates accelerating from rest through various angular velocity profiles. The objective is to gain an understanding of the connection among the prescribed kinematics and resulting vortex formation; a relationship which has not currently been thoroughly explored. The root-to-tip flow that is induced b...

We investigate the unsteady flow of a fish-inspired robot executing starts from rest, with the objective of understanding the connection among the kinematics, vortex formation, and acceleration performance. Several fish perform ``fast starts,'' where the body bends into a ``C'' or ``S'' shape while turning (phase I), followed by a straightening of...

Experiments were performed to investigate the flow In a Mach 2.9 shack wave turbulent boundary-layer interaction at a Reynolds number based on momentum thickness of 2400. The flow configuration was a nominally two-dimensional 24 deg compression ramp, which exhibited a separation bubble in the corner region. Mean flow quantities, including the veloc...

The characterization of the turbulence structure using statistical analysis 1 and a geo-metric packet-finding algorithm 2 is explored. We follow structures which have been identi-fied by the geometric packet-finding algorithm, using automated object segmentation and feature tracking software, 3, 4 and observe how these structures and their associat...

Preliminary experiments using PIV for the study of a Mach 7.2 turbulent boundary layer are reported. The roles of interval timing, and seeding density are discussed qualitatively, and recommendations are made for future investigations.

A study was conducted to demonstrate the low Reynolds number effects in a Mach-3 shock/turbulent boundary-layer interaction. The study showed the validation of the fluctuating wall pressure for the direct numerical simulation data. The study described the low Reynolds number effects by comparing the size of separation bubble and the wall pressure s...

We demonstrate that data from direct numerical simulation of turbulent boundary layers at Mach 3 exhibit the same large-scale coherent structures that are found in supersonic and subsonic experiments, namely elongated, low-speed features in the logarithmic region and hairpin vortex packets. Contour plots of the streamwise mass flux show very long l...

Experiments are performed to investigate the fluctuating wall pressure in a Mach 2.9 shock-wave turbulent boundary layer interaction with a low Reynolds number based on momentum thickness of 2400. This Reynolds number is accessible to present direct numerical simulations (DNS), so that the data can be used for DNS validation. The configuration stud...

We investigate experimentally the force generated by the unsteady vortex formation of low-aspect-ratio normal flat plates with one end free. The objective of this study is to determine the role of the free end, or tip, vortex. Understanding this simple case provides insight into flapping-wing propulsion, which involves the unsteady motion of low-as...

We use a direct numerical simulation database (Martin, JFM 2006) of
compressible turbulent boundary layers to develop tracking algorithms
for the turbulence structures. We use the pattern recognition and
tracking algorithm of Wang and Silver (IEEE Transactions on
Visualization and Computer Graphics, 1997) and incorporate the criteria
used by Ringue...

We utilize a direct numerical simulation database to characterize the
properties of coherent structures in supersonic turbulent boundary
layers at Mach numbers from 3 to 5. Tools to calculate the average
structure angle, convection velocity, and length scale are developed,
and the results show good agreement with the available experimental
data. We...

A direct numerical simulation database is used to characterize the structure of su-personic turbulent boundary layers at Mach numbers from 3 to 5. We develop tools to calculate the average properties of the coherent structures, namely, angle, convection ve-locity, and length scale, and show good agreement with the available experimental data. We fi...

Shockwave and turbulent boundary layer interactions (STBLI) result in intense localized heating rates and pressure loads, making them extremely important flow features that must be identified for engineering design. The absence of detailed and complete experimental and numerical data at the same flow and boundary conditions is one of the major stum...

Using a direct numerical simulation database, we present a preliminary
characterization of the properties of coherent structures in turbulent
boundary layers at Mach numbers from 0.3 to 7. The attributes of
organized turbulent motions, such as angle, length scale, convection
velocity, and internal structure, as well as their variation with Mach
num...

Flapping wings generate vortices, which are believed to be among the primary means used by insects to fly. The exact mechanism producing enough lift force to hover, however, remains a puzzle that researchers have tackled in various ways; here we shed additional light on the problem, using an evolutionary algorithm to maximize the lift produced by t...

Experiments were done to investigate the role of vortex formation in the drag force generation of low aspect ratio, normal flat plates starting from rest. This very simplified case is a first, fundamental step toward understanding the more complicated flow of hovering flight, which relies primarily on drag for propulsion. The relative importance of...

We present results from the application of a novel evolution strategy to the problem of lift maximization for an oscillating plate at 90 degrees angle of attack. We introduce a cost function measuring the average lift resulting from periodic oscillations, devised to minimize the effects of measurement errors. The plate is oscillated along one direc...

During acceleration from rest, an airfoil generates vorticity at its leading and trailing edges. The leading edge vortex (LEV) provides high lift during the transient period before it is shed. The dimensionless time at which the LEV stops entraining circulation is called the formation number (Gharib et al., J. Fluid Mech. 1998, vol. 360). Formation...

Experiments were conducted using a deep-channel viscometer, which consists of an annular region where the liquid is bounded by stationary inner and outer cylinders, a rotating floor, and a free surface. The deep-channel was originally devised for the low-speed, linear regime to measure the surface shear viscosity (mu^s) at a given uniform surfactan...

We perform experiments to investigate the unsteady wall-pressure behavior in a Mach 2.9 shock-wave turbulent boundary layer interaction. The flow configuration is a nominally two-dimensional 24^o compression ramp, and the Reynolds number based on momentum thickness is 2400. In contrast to measurements at higher Reynolds numbers (of order 10^4--10^5...