Article
Thermodynamics
Bahram Jalili, Majdeddin Emad, Payam Jalili, Davood Domiri Ganji, Salman Saleem, Elsayed M. Tag-eldin
Summary: This study investigates the convective flow of a constant, laminar, and incompressible viscous fluid over a moving plate with the assumption of nanoparticles, such as Al and Cu. The governing equations consider the effects of radiation, internal heat generation, and viscous dissipation factor. By using similarity transformations, the momentum and temperature PDEs are converted to nonlinear ODEs and solved using the Akbari-Ganji method (AGM), a new and effective semianalytic approach. Comparison with previous results shows good agreement. Increasing the suction parameter increases the velocity of the nanofluid while decreasing the temperature. The lambda slip term affects the velocity and temperature gradient, with velocity rising and temperature decreasing. The variations of temperature and velocity range from -0.5 to 1.5.
CASE STUDIES IN THERMAL ENGINEERING
(2023)
Article
Mechanics
Omar Kamal, Matthew T. Lakebrink, Tim Colonius
Summary: Linear input-output analysis is used to determine worst-case disturbances in a laminar base flow based on a generic forcing term. However, physically realizable worst-case disturbance problems lack a generic framework. In natural receptivity analysis, disturbances are forced by matching local solutions within the boundary layer to outer solutions. A scattering formalism is proposed to restrict the input forcing to realizable disturbances associated with plane-wave solutions of the outer problem. The method is validated through numerical simulations and provides insights into transition mechanisms.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Energy & Fuels
Tian-Wen Jiang, Zhong-Wei Huang, Jing-Bin Li, Yi-Su Zhou
Summary: The study utilizes LES and RNG k-epsilon model to analyze the flow characteristics inside the cone-straight nozzle, revealing the transition of flow from laminar to turbulent with increasing inlet velocity, with the main flow resistance mainly produced in the throat section.
Article
Mechanics
F. Capone, J. A. Gianfrani, G. Massa, D. A. S. Rees
Summary: The aim of this paper is to analyze how a downward vertical net mass flow affects the instability in a heated horizontal fluid-saturated porous layer. The strength of the downflow is represented by the Peclet number, Pe. The validity of the principle of exchange of stabilities is proven, followed by a linear instability analysis and a weakly nonlinear stability analysis to determine the critical Darcy-Rayleigh number and the smallest value of Pe for the onset of convection, respectively.
Article
Mechanics
Alexander J. Smits, Marcus Hultmark, Myoungkyu Lee, Sergio Pirozzoli, Xiaohua Wu
Summary: The new scaling shows a Reynolds-number-independent profile for all components of the Reynolds stress in the near-wall region of wall-bounded flows, highlighting the significance of wall shear stress fluctuations and the role of large eddies in determining the Reynolds number dependence of near-wall turbulence behavior.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Fluids & Plasmas
Yue Xiao, Yi Li, Moli Zhao, Shaowei Wang
Summary: This paper provides a mathematical description of the onset of instability for buoyancy-driven flow around a cone. The self-similar solutions of the basic flow are derived, and the linear instability properties are investigated using the Chebyshev collocation method. Primary instabilities on the cone surface are identified as type-I and type-II modes. Energy analysis reveals the dominant effects in different modes. This study is significant for understanding buoyancy-driven systems.
Article
Mechanics
G. G. Rooney
Summary: Dynamical constraints on the wall layer in turbulent pipe flow result in a narrow peak in the streamwise component of the turbulent Lamb vector near the wall, and a scaling relationship between the wall layer depth and the depth of the viscous sublayer. An approximation of the Lamb vector distribution, which is equivalent to the gradient of Reynolds stress, is proposed. Integration of the equation for streamwise mean flow allows for an expression of the velocity profile in the wall layer.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Michael Heisel, Charitha M. de Silva, Nicholas Hutchins, Ivan Marusic, Michele Guala
Summary: The statistical properties of prograde spanwise vortex cores and internal shear layers in high-Reynolds-number turbulent boundary layers are evaluated. Results show the importance of the local large-eddy turnover time in determining the strain rate confining the size of the vortex cores and shear layers. The study highlights the relevance of the turnover time and the Taylor microscale in explaining the interaction of coherent velocity structures in the boundary layer flows.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Yan Liu, T. Stoesser, H. Fang
Summary: This study investigates the effect of secondary currents on friction factor, statistics, and large-scale turbulent motion in partially filled pipes using large-eddy simulations. The results show that secondary currents originate from the corner between the free surface and the pipe walls, and their presence reduces the friction factor and the strength of near-wall structures. Therefore, partially filled pipe flows have lower drag and turbulent energy compared to fully filled pipe flows.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Multidisciplinary Sciences
Mohsan Hassan, Muhammad Ahsan, Usman, Metib Alghamdi, Taseer Muhammad
Summary: Shear thinning fluids with unique flow characteristics are widely used in the food and polymer industries. This study investigates the transport characteristics of a Powell Eyring fluid under different shear rates and calculates the rate of entropy generation. The results show that velocity and temperature profiles change with the time scale parameter.
SCIENTIFIC REPORTS
(2023)
Article
Meteorology & Atmospheric Sciences
Qingfang Jiang, Qing Wang
Summary: The study focused on the characteristics of a stable internal boundary layer (SIBL) offshore of Duck, North Carolina under the influence of offshore winds. The analysis showed that the offshore area can be divided into three zones, with local similarity theory applicable only in the nearshore zone. The advection of turbulence from land plays a significant role in the momentum and scalar budgets over the NSZ, while becoming less important but still non-negligible in the IOZ.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2021)
Article
Mechanics
Yue Xiao, Bin Zhang, Moli Zhao, Shaowei Wang
Summary: The linear instability of the buoyancy-driven flow adjacent to an inclined heated wall immersed in a thermally stratified medium is studied theoretically and numerically. The results demonstrate the significant influence of the tile angle and Prandtl number on the spatiotemporal properties of the flow.
Article
Mechanics
Alexander J. Smits
Summary: Our understanding of turbulent boundary layer scaling and structure has greatly advanced in the past few decades, thanks to the progress in numerical simulations and experimental methods.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Sourabh S. Diwan, Jonathan F. Morrison
Summary: The study proposed a three-layer asymptotic structure for turbulent pipe flow, revealing the existence of a Reynolds-number-invariant logarithmic region for the streamwise mean velocity and variance in terms of intermediate variables. The analysis determined the classical von Karman and Townsend-Perry constants from the intermediate-scaled log-law constants.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
D. Exposito, S. L. Gai, A. J. Neely
Summary: This study attempts to solve steady-state triple-deck equations for supersonic flow past a compression corner, and compares the results with previous methods. The study reveals the presence of spurious wave-packets, which may be caused by the numerical method employed.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Green & Sustainable Science & Technology
Feng Guo, Jakob Mann, Alfredo Pen, David Schlipf, Po Wen Cheng
Summary: Lidar-assisted wind turbine control has been proven to be beneficial for reducing turbine load. However, previous studies have mainly focused on standard turbulence parameters and ignored the temporal evolution of turbulence. This study presents a simple method to extend the turbulence model using a space-time spectral velocity tensor and emphasizes the importance of considering the temporal evolution of turbulence for assessing lidar wind preview quality.
Article
Environmental Sciences
Marcos Paulo Araujo da Silva, Francesc Rocadenbosch, Joan Farre-Guarne, Andreu Salcedo-Bosch, Daniel Gonzalez-Marco, Alfredo Pena
Summary: This study presents a parametric-solver algorithm for estimating atmospheric stability and friction velocity. The algorithm was validated by comparing results with reference data, and showed satisfactory agreement.
Article
Meteorology & Atmospheric Sciences
Alfredo Pena, Jeffrey D. Mirocha, M. Paul van der Laan
Summary: This study evaluates the wind-farm parameterization of the Weather Research and Forecasting Model and finds that it shows excellent agreement in predicting velocity within the turbine area. However, there are discrepancies in predicting turbulence kinetic energy (TKE) due to the requirement of higher TKE at the turbine position in mesoscale simulations. The impact of inversion height and strength is small, while resolution has a low impact on large-eddy simulations but a high impact on mesoscale simulations.
MONTHLY WEATHER REVIEW
(2022)
Article
Green & Sustainable Science & Technology
Basem Elshafei, Alfredo Pena, Atanas Popov, Donald Giddings, Jie Ren, Dong Xu, Xuerui Mao
Summary: In the pre-construction of wind farms, wind resource assessment plays a crucial role. Lidar measurements provide high-fidelity data, but they are expensive and sparse. On the other hand, Weather Research and Forecasting models generate continuous data with lower accuracy. To address this, a hybrid approach combining measurements and numerical simulations is proposed. The proposed method, evaluated using wind speed data along the coast of Denmark, achieves 58% more accurate results than the industrial standard method with minimal increase in computational cost. The RMSE of the proposed method ranges between 0.35 and 0.52 m/s.
Article
Green & Sustainable Science & Technology
Alessandro Sebastiani, Alfredo Pena, Niels Troldborg
Summary: This study proposes a new methodology for power performance evaluation of wind turbines operating under waked conditions. Multivariate power curves, utilizing wind speed and turbulence measurements, are defined using polynomial regression models. Results show that the multivariate power curves outperform the IEC standard power curve, with a significant reduction in error of up to 88% for in-wake cases.
Article
Meteorology & Atmospheric Sciences
Rogier Floors, Ib Troen, Alfredo Pena
Summary: Modifying the model in the Wind Atlas Analysis and Application program (WAsP), we account for local atmospheric stability parameters, which significantly improves the vertical extrapolations of Weibull wind speed distribution parameters. The model is validated at six locations in northwestern Europe, showing improved estimations of power density distributions by reducing the percentage error from 5.2% to 3% when using the modified model and temperature scale derived from either observations or mesoscale/reanalysis output.
BOUNDARY-LAYER METEOROLOGY
(2023)
Article
Meteorology & Atmospheric Sciences
Sven-Erik Gryning, Ekaterina Batchvarova, Rogier Floors, Christoph Muenkel, Lise Lotte Sorensen, Henrik Skov
Summary: The depth of the aerosol layer at the Villum Research Station in the high Arctic is analyzed using 8 years of ceilometer observations and 1 year of wind lidar data. Two methods are used to determine the depth based on the attenuated backscatter profile. The analysis shows that the aerosol layer depth is typically asymptotic to 230 m and varies little between winter and summer.
INTERNATIONAL JOURNAL OF CLIMATOLOGY
(2023)
Article
Environmental Sciences
Marcos Paulo Araujo da Silva, Andreu Salcedo-Bosch, Francesc Rocadenbosch, Alfredo Pena
Summary: We reexamine two recent methodologies, the 2D method and Hybrid-Wind (HW), based on Monin-Obukhov Similarity Theory (MOST), which aim to estimate Obukhov length, friction velocity, and kinematic heat flux within the surface layer using wind-speed profile measurements. Both methods are compared using synthetic and observational data. A procedure to generate synthetic noise-corrupted wind profiles is also presented. The 2D algorithm outperforms the HW method in estimating the three parameters, making it a prominent method for surface-layer parameter estimation.
Article
Green & Sustainable Science & Technology
Vanesa Magar, Alfredo Pena, Andrea Noemi Hahmann, Daniel Alejandro Pacheco-Rojas, Luis Salvador Garcia-Hernandez, Markus Sebastian Gross
Summary: This article provides a comprehensive overview of wind energy development in Mexico, including the current situation, obstacles faced, and proposed solutions. It emphasizes the importance of wind energy in addressing climate change and achieving sustainable development goals. The article discusses the reasons behind Mexico's lag in wind energy development and explores the potential of community wind energy projects as a solution. It also highlights the need to consider microscale effects in wind energy feasibility studies and proposes solutions for addressing challenges such as future climate change scenarios, grid planning, and vulnerability to tropical storms.
Article
Green & Sustainable Science & Technology
Wei Fu, Alessandro Sebastiani, Alfredo Pena, Jakob Mann
Summary: Through simulations and field measurements, this study examines the impact of nacelle lidar scanning strategies on the accuracy and uncertainty of turbulence estimations. The findings indicate that a nacelle lidar system with at least six beams, including one with a different opening angle, is needed for accurate estimation of Reynolds stresses. Increasing the opening angle improves accuracy and reduces uncertainty for transverse components, while increasing the measurement distance has the opposite effect. Overall, a six-beam continuous-wave lidar with a large opening angle and close measurement distance provides the best estimations of Reynolds stresses.
WIND ENERGY SCIENCE
(2023)
Proceedings Paper
Energy & Fuels
Alfredo Pena, Oscar Garcia-Santiago, Branko Kosovic, Jeffrey D. Mirocha, Timothy W. Juliano
Summary: Wind-farm parametrizations are important for studying the impact of wind farms on the local climate and other wind farms. This study evaluates the accuracy of the Fitch scheme, an in-built wind-farm parametrization in the WRF model, through simulating a small wind farm. The results show that the simulations at lower resolution are in better agreement with high-resolution simulations with large-eddy simulation (LES).
WAKE CONFERENCE 2023
(2023)
Article
Green & Sustainable Science & Technology
Maarten Paul van der Laan, Oscar Garcia-Santiago, Mark Kelly, Alexander Meyer Forsting, Camille Dubreuil-Boisclair, Knut Sponheim Seim, Marc Imberger, Alfredo Pena, Niels Normark Sorensen, Pierre-Elouan Rethore
Summary: This paper presents a RANS method for simulating the interaction between offshore wind farms. The proposed method includes a steady-state atmospheric inflow and a novel wind farm parameterization model, which reduces the computational time and produces results consistent with measurements.
WIND ENERGY SCIENCE
(2023)
Article
Green & Sustainable Science & Technology
Wei Fu, Alfredo Pena, Jakob Mann
Summary: This study investigates the estimation of turbulence by different wind profilers deployed on a wind turbine. Results show that only the SpinnerLidar is capable of retrieving all components of the Reynolds stress tensor. For the two- and four-beam lidars, different methods are proposed to compute the along-wind velocity variance, and using the SpinnerLidar's Doppler spectra helps reduce the systematic error in turbulence estimates.
WIND ENERGY SCIENCE
(2022)
