Article
Mechanics
L. R. Gareev, J. S. Zayko, A. D. Chicherina, V. V. Trifonov, A. Reshmin, V. V. Vedeneev
Summary: This paper studies the development of perturbations in a submerged air jet with a round cross-section and a long laminar region. The results of experiments are in good agreement with theoretical calculations, demonstrating that small perturbations closely follow the predictions of inviscid linear stability theory.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Eirik Aesoy, Jose G. Aguilar, Nicholas A. Worth, James R. Dawson
Summary: The study investigates the hydrodynamic response of an axisymmetric jet placed at various positions in a standing wave oriented normally to the jet. Different modes of fluctuations are excited at velocity and pressure nodes, causing asymmetric forcing and bifurcation of momentum streams between the nodes. The asymmetrical response can be approximated by superposition of boundary conditions at pressure and velocity nodes, with the jet symmetry and momentum spreading proportional to the transverse acoustic velocity magnitude.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Multidisciplinary
Wenchao Jia, Meixia Chen, Kun Xie, Zhiwei Zhou
Summary: A unified hybrid analytical-numerical method is proposed for vibration analysis of stiffened hulls coupled with non-axisymmetric internal structures. The method decomposes the coupled system into the submarine hull and internal structures, and further divides the stiffened hull into ring stiffeners, bulkheads, and shell segments. The non-axisymmetric interior structures are analyzed using the finite element method, while the shell strips and axisymmetric reinforcements are described using the Flugge formula and power series method. A precise coupling method is proposed to synthesize the receptance functions at coupling nodes, considering all 6 degrees of freedom. The method is verified through experiments and compared with results obtained from the finite element method.
APPLIED MATHEMATICAL MODELLING
(2023)
Article
Mechanics
Arun Kumar Perumal, Yu Zhou
Summary: This study experimentally manipulates a turbulent round jet with Reynolds number of 8000, investigating the effect of five control parameters on the decay rate of the jet-centerline mean velocity. Different flow structures for various minijet configurations are proposed, and three distinct mechanisms of highly effective manipulation are identified. The optimal parameters for maximum decay rate occurrence do not vary with the minijet number, but the penetration depth of the minijet does.
Article
Mechanics
Khashayar F. Kohan, Susan J. Gaskin
Summary: This study investigates the effect of a zero-mean-flow turbulent ambient on the geometry of the turbulent/turbulent interface (TTI) of an axisymmetric jet and compares it with the traditional turbulent/non-turbulent interface (TNTI). The results show that the ambient turbulence enhances radial transport of concentration and scalar fluctuations within the jet, resulting in steeper mean and root-mean-square scalar conditional jumps across the TTI layer compared with those of the TNTI. The presence of ambient turbulence also stretches and corrugates the interface surface area.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Xiangru Li, Xuecheng Wu, Luhan Liu, Xiwen Zhang, Pengfei Hao, Feng He
Summary: In this study, the acoustic resonance mechanism of different axisymmetric screech modes of underexpanded jets impinging on an inclined plate is experimentally investigated. It is found that the nozzle-to-plate distance and the impingement angle have significant effects on the screech modes. A new screech mode (A3) is observed, in addition to the A2 mode. The results also show that the influence of the plate on the shock cell structures of jets becomes more apparent as the Mach number increases, resulting in the presence of the second suboptimal peaks in the axial wavenumber spectra.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
B. Gungordu, M. Jabbal, A. A. Popov
Summary: In this study, the coupled structural-fluidic-acoustic modelling of piezoelectric diaphragm driven synthetic jet actuators is conducted computationally for the first time to demonstrate the importance of piezoelectric diaphragm structural modelling and the effects of acoustics coupling on the accuracy of synthetic jet exit jet velocity.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2023)
Article
Engineering, Mechanical
Lianshan Lu, Dong Li, Zhenhui Zhang, Yin Yang, Dawei Liu, Yang Tao, Bo Lu
Summary: This paper designs an acoustic synthetic jet actuator that can generate multiple jets with one diaphragm. The governing parameters are given by theoretical derivation and the velocity characteristics of the jets are measured, showing the applicability of this technology to turbulent boundary layer flow control.
Article
Engineering, Aerospace
David Leiser, Fabian Hufgard, Christian Duernhofer, Stefan Loehle, Stefanos Fasoulas
Summary: This paper proposes a methodology to scale the stagnation point plasma conditions of an axially symmetric body to a two-dimensional planar body, providing a theoretical basis for the testing of material samples under thermochemical loads combined with aeromechanical loads, and the experimental verification has been conducted.
Article
Mechanics
O. O. Ivanov, D. A. Ashurov, L. R. Gareev, V. V. Vedeneev
Summary: This study identifies the non-modal "lift-up" growth mechanism through experiments and confirms that the development of disturbances qualitatively corresponds to the theoretically calculated optimal perturbations. The features of the transition to turbulence caused by non-modal growth are discussed.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
Tengfei Cai, Jin-Tae Kim, Shyuan Cheng, Fei Ma, Leonardo P. Chamorro
Summary: In this experimental study, the effects of various axisymmetric orifice geometries on jet characteristics at Reynolds number of approximately 10^5 were explored. The thickness and divergence angle of the orifices were found to impact velocity profiles and mixing rates in the near region, highlighting the influence of geometry on turbulent structures and flow behavior.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2021)
Article
Mechanics
Milad Samie, Vlad Aparece-Scutariu, Philippe Lavoie, Dong-hyuk Shin, Andrew Pollard
Summary: This study uses direct numerical simulation to investigate three-dimensional vortical and very-large-scale coherent structures in a turbulent round jet at a Reynolds number of 7300. The results show the importance of horseshoe vortices in the jet and the existence of symmetric and asymmetric horseshoe vortices that affect the high and low momentum regions in the flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Energy & Fuels
Marcus D. F. B. da Costa, Jose J. S. de Figueiredo, Lucas Rautino, Juliana Furtado, Rafael Lima
Summary: In this study, the behavior of porous layered rocks in seismic wave propagation research was investigated through experimental ultrasonic measurements. The results showed significant deviations from theoretical predictions, particularly for samples with a higher number of layers, due to pressure-related effects.
GEOMECHANICS FOR ENERGY AND THE ENVIRONMENT
(2023)
Article
Engineering, Mechanical
Andrea Palumbo, Luigi de Luca
Summary: This paper presents a joint experimental and numerical characterization of double-orifice synthetic jet actuators for flow control. The study found that the distance between the orifices has a significant impact on the flow field generated by the device, and proposed a novel classification of the main regions of dual synthetic jets. This work aims to provide guidelines for the design of synthetic jet arrays for separation control and impinging configurations.
Article
Mechanics
Michael N. Stavropoulos, Matteo Mancinelli, Peter Jordan, Vincent Jaunet, Joel Weightman, Daniel M. Edgington-Mitchell, Petronio A. S. Nogueira
Summary: Spatial linear stability analysis is used to study the axisymmetric screech tones generated by twin converging round nozzles. Different waves supported by the flow at different conditions are identified using vortex-sheet and finite-thickness models. The frequency-wavenumber regions at which the upstream-propagating guided jet modes are neutrally stable vary with solution symmetry, jet separation, S, and the velocity profile. Screech-frequency predictions from both models agree well with experimental data, but the predictions from the finite-thickness model match the measured screech tones better than the vortex sheet. The present results suggest that the feedback loop generating these screech tones is similar to that observed for single-jet resonance.
JOURNAL OF FLUID MECHANICS
(2023)