Islam Ramadan

• PhD
• Assistant professor at Université de Poitiers

The present study provides an experimental method for measuring acoustic velocity components (amplitude and spatial phase shift) in the presence of turbulent flows using either low-frequency particle image velocimetry (PIV) or laser Doppler velocimetry (LDV). The approach leverages compressed sensing (CS) principles to overcome the limitations of c...

This study focuses on the influences of natural convection on the temperature distribution in a compact thermoacoustic coaxial heat pump. The behaviour of this device is quite consistent with results of Rott's linear theory of thermoacoustics, but early measurements reveal a non-uniformity of the temperature along the transverse dimension of the co...

Increasing the capacity of thermoacoustic machines (engines or refrigerators) requires increasing the diameter of the regenerator, which may result in non-uniform temperature distributions inside the regenerator. In the current study, the temperature is measured at different radial and axial locations inside the regenerator of a thermoacoustic refr...

Measuring the acoustic velocity is crucial for expressing certain physical quantities like acoustic intensity or liner impedance. However, measuring acoustic velocity, using non-intrusive techniques, in the presence of turbulent flow is quite challenging. A signal processing technique is proposed to estimate the acoustic velocity from the velocity...

A toroidal-topology traveling-wave thermoacoustic electric generator (TWTEG) is developed. It consists of a traveling-wave thermoacoustic engine, two linear alternators connected in parallel, and sets of variable resistive-capacitive (R-C) external electric loads, in conjunction with accessories and instrumentation required for experimental investi...

Increasing the capacity of thermoacoustic machines (engines or refrigerators) requires increasing the diameter of the regenerator, which may result in non-uniform temperature distributions inside the regenerator. In the current study, the temperature is measured at different radial and axial locations inside the regenerator of a thermoacoustic refr...

This study focuses on the influences of natural convection on the temperature distribution in a compact thermoacoustic coaxial heat pump. The behaviour of this device is quite consistent with results of Rott's linear theory of thermoacoustics, but early measurements reveal a non-uniformity of the temperature along the transverse dimension of the co...

The present study provides an experimental method for measuring acoustic velocity components (amplitude and spatial phase shift) in the presence of turbulent flows using either low-frequency Particle Image Velocimetry (PIV) or Laser Doppler Velocimetry (LDV). The approach leverages Compressed Sensing (CS) principles to overcome the limitations of c...

The pressure losses through sharp-edged, multi-orifice circular perforated plates with two different ratios of plate thickness to orifices’ diameter are experimentally investigated using both water and dry air as working fluids. The choice of a thickness for which fluid-dynamic instabilities related to flow reattachment are known to occur allows to...

Phase-locked PIV measurement technique is used to estimate the acoustic velocity in the presence of turbulent flow inside a rectangular duct. The acoustic field is generated by compression drivers mounted on the sides of a rectangular duct. The PIV measurements are synchronized with the compression drivers. The measured velocity fields can be decom...

The current study reports an experimental investigation of flow regimes for acoustically oscillating flows in the near-wall region of a resonator. Particle Image Velocimetry (PIV) is used to measure axial and transverse velocity components inside an empty square resonator over the acoustic cycle for a wide range of Reynolds numbers and at a high Wo...

Noise generation by low Mach number air flows through circular orifices in rectangular ducts is investigated. In particular, the influence of the number and position of the orifices maintaining a constant flow area is addressed. A review of the available theories suggests a certain importance of such parameters in the excitation of higher-order aco...

An experimental campaign on aerodynamic noise generation by orifice plates in rectangular ducts for low Mach number flows is carried. The test plant allows for the measurement of the total emitted acoustic power both upstream and downstream of the orifice plates for varying mass flow rates through the 2N-Port method. A modal decomposition for the f...

La mesure par Vélocimétrie par Images de Particules (Particle Image Velocimetry - PIV) est une méthode de mesure optique non intrusive qui donne une cartographie de la vitesse du fluide ensemencé. Cette technique est utilisée pour mesurer la cartographie de la vitesse particulaire dans un conduit de section rectangulaire. Une chambre de compression...

A calculation method is proposed to investigate trapped modes in a rigid waveguide with rigid obstacles in the presence of non-potential steady mean flow in a two-dimensional coordinate system. This method facilitates the investigation of trapped modes in the presence of non-potential flow. A coupled calculation method that combines computational f...

The aim of this study is to investigate the oscillating flow velocity field at the exit of different stacked mesh grid regenerators using Particle Image Velocimetry measurements. Twelve different experimental cases are discussed, yielding oscillating flow fields at the exit of four kinds of regenerators for different acoustic levels. The regenerato...

Thermoacoustic refrigeration technology is a green alternative for the conventional refrigeration system in vehicles. The former uses environmentally friendly inert gases whereas the latter uses chemical refrigerants that can have severe impacts on the environment. In order to apply thermoacoustic technology in the automobile industry, the size and...

This study aims at exploring the potential generation of natural convective flows in thermoacoustic devices. To this effect, two thermoacoustic setups are considered without acoustic oscillations, each setup thus constituting a cavity filled with air and comprising a porous medium heated on one of its ends. In the first configuration, the porous me...

Regenerators (often consisting in stack mesh-wires) and heat exchangers are the core of thermoacoustic devices and, as such, key elements for the efficiency of these systems. In this study, the oscillating flow velocity field at the exit of different regenerators has been measured using Particle Image Velocimetry (PIV) system. Three different mesh...

Standing-wave thermoacoustic engines and refrigerators utilize gas oscillations and stacks to produce thermoacoustic effects. The flow morphology at the inlets/exits of the stack affects the heat transfer processes and the viscous flow losses in the heat exchangers. In this work, the flow morphology and the size of the disturbance zone are investig...

La vélocimétrie par images de particules et l'anémométrie laser Doppler sont utilisées pour étudier le vent acoustique de Rayleigh dans un moteur thermoacoustique. Le vent acoustique est un écoulement stationnaire de second ordre superposé à l’écoulement acoustique oscillant du premier ordre. La mesure de ce type d’écoulement, même dans un résonate...

Thermoacoustic systems (engines or refrigerators) convert any source of heat energy, including solar energy and waste heat, into electricity or cooling effect. These systems are reliable and durable as they operate with few or no moving parts and they employ environmentally-friendly gases without gaseous emissions. However, thermoacoustic systems s...

The influence of both the natural convection and end-effects on Rayleigh streaming pattern in a simple standing-wave thermoacoustic engine is investigated experimentally at different acoustic levels. The axial mean velocity inside the engine is measured using both Laser Doppler Velocimetry and Particle Image Velocimetry. The mean flow patterns are...

Non-linearities associated with the oscillating flow contribute in deteriorating the performance of thermoacoustic systems. Turbulence generation is one of these non-linearities which dissipates the acoustic energy into a non-useful form of energy (heat). In this work, the transition to turbulence in oscillating flow inside a square duct is investi...

Thermoacoustic engines suffer from many non-linearities that deteriorate the overall performance. Streaming phenomenon is one of these non-linearities which can affect the performance by convecting a certain amount of heat. In this study, the axial mean velocity distribution inside a basic standing-wave thermoacoustic engine is measured using Laser...

Concerns about global warming have encouraged the interest in hydrocarbon combustion techniques that allow easy capture of carbon dioxide. One technique for achieving this objective is through the use of pure oxygen instead of air for combustion or what is called oxy-combustion carbon capture technology. The main goal of the manuscript is to study...

Streaming mechanism in thermoacoustic Stirling engine involves the generation of a nonzero time-averaged mass flux within its closed-loop path, which convects heat from the hot heat exchanger to the secondary heat exchanger through the thermal buffer tube. This non-linear acoustic mechanism significantly dissipates heat and reduces the engine effic...

Concerns about global warming have encouraged interest in hydrocarbon combustion techniques that allow easy capture and sequestration of carbon dioxide. One method of achieving this objective is through the use of post-combustion CO2 capture and sequestration. In this work, Compressed Natural Gas (CNG) flames were burned in confined diffusion situa...

Concerns about global warming have encouraged interest in hydrocarbon combustion techniques that allow easy capture and sequestration of carbon dioxide. One method of achieving this objective is through the use of post-combustion CO 2 capture and sequestration. In this work, Compressed Natural Gas (CNG) flames were burned in confined diffusion situ...