Article
Engineering, Chemical
Xiaopei Yang, Jun Wang, Boyan Jiang, Zhi'ang Li, Qianhao Xiao
Summary: This study investigates the effects of sawtooth riblets on NACA4412 airfoil at low Reynolds number, focusing on the impact of riblet length and height on aerodynamic performance. Results show that the most effective riblet length is 0.8 chord, leading to significant improvements in lift and drag coefficients, while the most effective height for a riblet with a length of 0.5 chord is 0.6 mm. Riblets can facilitate a greater improvement in airfoil performance at larger angles of attack.
Article
Chemistry, Multidisciplinary
Lorenzo Cacciatori, Carlo Brignoli, Benedetto Mele, Federica Gattere, Celeste Monti, Maurizio Quadrio
Summary: This study assesses for the first time the effects of riblets on the total aerodynamic drag of a low-speed UAV using RANS simulations. The results show that installing riblets with optimal size can significantly reduce the drag coefficient of the aircraft, and installing riblets on the wing can further decrease the drag, improving the cost-benefit ratio.
APPLIED SCIENCES-BASEL
(2022)
Article
Engineering, Mechanical
Vikas Sharma, Sushanta Dutta
Summary: Flow alteration using the bio-inspired riblet structure is a fascinating field of study resulting in drag benefits. Riblets have no power requirement being a passive method. This work aims to study the effect of riblets on flow and drag behavior using both experimental and numerical analysis.
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
(2023)
Article
Engineering, Civil
Vikas Sharma, Sushanta Dutta
Summary: This study aims to improve the aerodynamic performance of navigating objects using bio-inspired surface modification. By investigating the effect of different modified surface structures on drag and flow characteristics, the results show that riblets effectively reduce drag coefficient, decrease energy consumption, and increase navigating speed.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2022)
Article
Thermodynamics
Shabnam Raayai-Ardakani
Summary: Periodic and symmetric two-dimensional textures with various cross-sectional profiles are studied to improve the physical response of surfaces. A polynomial framework is proposed to define and measure the profiles of these textures, and their hydrodynamic frictional response is tested. Experimental and numerical results show that textures with concave profiles and height-to-half-spacing ratios of lower and equal to unity offer lower torque compared to smooth surfaces and triangular textures. Polynomials of second order provide sufficient response range without the need for higher order or more complex polynomials.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2022)
Article
Engineering, Chemical
Muhammad Uzair, M. Danyal Qasim, M. Aashan Bhatti, Ali Abbas Zaidi, John J. Molina, Ryoichi Yamamoto, Adnan Hamid
Summary: The recently updated Smooth Profile Method (SPM) is validated for rigid particles settling in a Newtonian fluid. Non-spherical particles, including regular and irregular shapes, are generated by joining spherical beads. Drag and lift coefficients are calculated for regular-shaped particles, and good agreement with literature is observed. New correlations for fiber, disk, and scalene prolate particles are suggested.
Article
Green & Sustainable Science & Technology
Shaotao Fan, Xiangxi Han, Youhong Tang, Yiwen Wang, Xiangshao Kong
Summary: This study proposes a novel biomimetic turbulent drag reduction topology inspired by the special structure of shark skin. The excellent drag reduction performances of the optimized ribletted surfaces are verified by large eddy simulation. The designed riblets exhibit higher turbulent drag reduction behavior and the effects of the riblets on fluid flow behavior and drag reduction mechanisms are discussed.
Article
Thermodynamics
Jiansheng Wang, Jianan Ge, Yuntian Fan, Yuguo Fu, Xueling Liu
Summary: In this paper, the flow behavior in a rectangular channel with miniature riblets (MRs) is investigated numerically. The results show that the MRs effectively reduce drag and improve flow stability, but they also lead to a deterioration in heat transfer performance.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2022)
Article
Engineering, Chemical
Yan Xia, Zhaowu Lin, Yu Guo, Zhaosheng Yu
Summary: Data from IR-DNSs of upward turbulent channel flow laden with finite-size heavy particles are used to develop improved drag correlations accounting for turbulence effects. The contribution of drag nonlinearity to drag enhancement is analyzed, and several turbulence correction models are presented. Turbulent intensity, particle size, and slip velocity are found to be the most important factors in modeling the effect of turbulence on particle drag.
Article
Mechanics
Hao Wang, Yitong Fan, Zhenguo Yan, Weipeng Li
Summary: Different from conventional streamwise-aligned riblets, converging and diverging (C-D) riblets arranged obliquely along the main-flow direction induce a large-scale secondary flow to modulate or control existing large-scale vortical structures in wall turbulence. Direct numerical simulations show that C-D riblets can reduce skin-friction drag but increase pressure drag, resulting in an overall increase in total drag. Detailed flow-field analysis reveals modifications in velocity, pressure, Reynolds stresses, and turbulence kinetic energy distributions due to the presence of C-D riblets. Examination of turbulence structures over the C-D riblets is conducted through instantaneous flow-fields and two-point correlations.
Article
Nanoscience & Nanotechnology
ZiDan Zhou, ShengKun Wang, ZeXiang Yan, DaoYuan Wang, JinJun Deng, Yang He, WeiZheng Yuan
Summary: Riblets inspired by shark skin show great potential in reducing air drag in various industries, with blade riblets currently reaching up to 11% drag reduction. A study introduced multilayer hierarchical riblets (MLHRs) as a method to further improve drag reduction, achieving up to 16.67% reduction in a closed air channel experiment.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Mechanics
Tongbiao Guo, Jian Fang, Ji Zhang, Xinliang Li
Summary: In this paper, the impact of convergent-divergent riblets on a supersonic turbulent boundary layer is examined using direct numerical simulations. The riblets induce spanwise heterogeneity and successfully reduce the area of the separation zone.
Article
Mechanics
Marwa Fakhfekh, Wael Ben Amira, Malek Abid, Aref Maalej
Summary: In this study, the mean deflection evolution of a flexible rotor blade is examined using a coupled model based on Navier-Stokes equations for fluid flow and linear elasticity equations for blade deformation. The elastic behavior of the flexible rotor blade is characterized under different parameter ranges, and the vorticity field is compared with that of a rigid rotor. The effect of pitch, tip speed ratio (or frequency), and its sign on blade deformation is investigated, revealing the non-monotonic relationship between deformation and rotation frequency and pitch angle. Additionally, the flexible rotor demonstrates the ability to develop a vortex ring state under specific conditions, which is not observed in the rigid rotor.
Article
Engineering, Aerospace
Monami Sasamori, Seigo Koga, Mitsuru Kurita
Summary: A method for estimating the drag reduction performance of riblets installed on aircraft surfaces was extended to consider the effect of pressure gradient. The study combined wind tunnel test data and computational fluid dynamics analysis to estimate the effectiveness of riblets on arbitrary aircraft surfaces. Results showed that the pressure gradient has a small impact on the overall riblet performance.
JOURNAL OF AIRCRAFT
(2022)
Article
Mechanics
Xin-wei Wang, Zi-ye Fan, Zhan-qi Tang, Nan Jiang
Summary: Experimental measurements using TR-PIV were conducted for turbulent boundary layer over smooth, superhydrophobic, and superhydrophobic-riblets surfaces. A drag reduction of about 22.1% was achieved on the superhydrophobic-riblets surface compared to 18.7% on the superhydrophobic surface. Large-scale structures over different surfaces were analyzed to show that the hairpin packets on the superhydrophobic-riblets surface were smaller and weaker than those on the smooth surface, but surpassed them in scale and strength in certain regions.
JOURNAL OF HYDRODYNAMICS
(2021)
Article
Computer Science, Interdisciplinary Applications
J. C. Brandle de Motta, P. Costa, J. J. Derksen, C. Peng, L-P Wang, W-P Breugem, J. L. Estivalezes, S. Vincent, E. Climent, P. Fede, P. Barbaresco, N. Renon
COMPUTERS & FLUIDS
(2019)
Article
Mechanics
H. O. G. Benschop, A. J. Greidanus, R. Delfos, J. Westerweel, W-P Breugem
JOURNAL OF FLUID MECHANICS
(2019)
Article
Mechanics
Souvik Ghosh, Jean-Christophe Loiseau, Wim-Paul Breugem, Luca Brandt
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2019)
Article
Thermodynamics
Tariq Shajahan, Wim-Paul Breugem
FLOW TURBULENCE AND COMBUSTION
(2020)
Article
Thermodynamics
C. Reurings, S. Koussios, O. K. Bergsma, W. -P. Breugem, K. Vergote, L. Paeshuyse, R. Benedictus
HEAT AND MASS TRANSFER
(2020)
Article
Thermodynamics
G. M. Ozkan, G. E. Elsinga, W-P Breugem, D. Stuebing, K. J. Reynolds, J. Westerweel
Summary: Experimental investigation on the effect of drag reducing riblets on the flow structure in a turbulent boundary layer was conducted. Results show that riblets significantly reduce turbulent structures compared to a smooth flat plate, as indicated by lower turbulent kinetic energy and Reynolds shear stress over the riblets.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2021)
Article
Mechanics
Hassan Nemati, Wim-Paul Breugem, Marcel Kwakkel, Bendiks Jan Boersma
Summary: The presence of bubbles in vertical channels flowing downward causes turbulent modulation, resulting in significant modification of the mean velocity profile and accumulation of bubbles in the core region with a bubble-free layer near the wall. The presence of bubbles also promotes turbulence in the core region, enhancing turbulent kinetic energy. Additionally, the size of bubbles affects the velocity fluctuations, with wall-normal and spanwise fluctuations decreasing for smaller bubbles in the near-wall region.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2021)
Article
Engineering, Environmental
O. J. Kramer, C. van Schaik, J. J. Hangelbroek, P. J. de Moel, M. G. Colin, M. Amsing, E. S. Boek, W. P. Breugem, J. T. Padding, J. P. van der Hoek
Summary: A sensor based on Archimedes' principle was developed to obtain the hydraulic state gradient in liquid-solid fluidised bed reactors, which can determine particle size and voidage. Experimental results indicate that the sensor is a more time-effective method for predicting the hydraulic state of the fluidised bed.
JOURNAL OF WATER PROCESS ENGINEERING
(2021)
Article
Physics, Fluids & Plasmas
Yavuz Emre Kamis, Huseyin Burak Eral, Wim-Paul Breugem
Summary: The study demonstrates that temperature modulation can effectively control the breakup of a jet, influencing the formation of droplets in terms of length and size distribution. The surface tension-gradient forces play a key role in the breakup process, with their impact varying depending on the strength of the thermal modulation.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Physics, Fluids & Plasmas
T. J. J. M. van Overveld, M. T. Shajahan, W-P Breugem, H. J. H. Clercx, M. Duran-Matute
Summary: When two spherical particles submerged in a viscous fluid are subjected to an oscillatory flow, they align themselves perpendicular to the flow direction, leaving a small gap between them. Through numerical simulations, it has been found that the particles oscillate both parallel and perpendicular to the oscillating flow. The mean gap between the particles depends on the boundary layer thickness and the streamwise excursion length. In the presence of bottom friction, particle rotation increases and the gap widens. This study highlights the importance of simulating the particle motion with all degrees of freedom.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Mechanics
Shravan K. R. Raaghav, Christian Poelma, Wim-Paul Breugem
Summary: Path instabilities of a sphere rising or falling in a quiescent Newtonian fluid have been experimentally studied. The study aims to shed light on the path instabilities for which previous studies disagree. The experimental results agree with literature for the low Galileo number range, but show some disagreements for the higher Galileo number range. Additionally, some phenomena that were only observed in numerical simulations have been observed experimentally for the first time.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2022)
Article
Mechanics
T. J. J. M. van Overveld, W-P Breugem, H. J. H. Clercx, M. Duran-Matute
Summary: This paper investigates the dynamics of spherical particles in oscillating flows. It is found that the dynamics of particle pairs in oscillating channel flows are fundamentally different from those in oscillating boxes due to the presence of a Stokes boundary layer. The results show that the oscillating channel flow and the oscillating box are only equivalent in a limited region of the parameter space.
Article
Mechanics
Yavuz Emre Kamis, Suriya Prakash, Wim-Paul Breugem, Hueseyin Burak Eral
Summary: We experimentally and numerically investigate the dynamics of a liquid jet ejected from a rotating nozzle with the breakup controlled by a vibrating piezo element. By quantifying the fictitious forces, we can estimate the intact length of the jet and the size distribution of the drops formed during breakup. We also find that the presence of these fictitious forces can destabilize high-frequency perturbations that would otherwise be stable without stretching.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Geert H. Keetels, Julien Chauchat, Wim-Paul Breugem
Summary: Reliable prediction of erosion rate of sediment beds is crucial for coastal and river engineering applications. However, the theoretical understanding of scaling relations, particularly for low and high Shields number conditions, is still insufficient. This study investigates the erosion process by analyzing the phase-averaged turbulent kinetic energy (TKE) equations and revealing various TKE modulation mechanisms at high Shields numbers and concentrations. Two scaling laws are derived and validated against extensive experimental data.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Tariq Shajahan, Wim-Paul Breugem
Summary: Particle-resolved direct numerical simulations were conducted to study the gravitational settling of solid spheres in a viscous fluid. The study found that the suspension microstructure and dynamics are mainly determined by the bulk concentration, with distinct settling regimes at different concentrations. Hindered settling and the presence of kinematic waves were also observed.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)