Miguel R. Visbal's research while affiliated with Air Force Research Laboratory and other places

... Pressure is a thermodynamic property that plays a key role in fluid mechanics. It is of utmost importance in aerodynamic load prediction [1,2,3], noise generation [4,5], flow instability and turbulence [6,7,8], and flow control [9]. The increase of time resolution in velocity field measurements during the last decade has opened the path to obtaining instantaneous pressure fields by combining experimental data with the flow governing equations [10,11]. ...

... This can significantly constrain the design of an AUV by determining manufacturing costs, durability, mission envelope etc., and thus demonstrates the necessity of finite flipper analysis. Contemporary literature on finite wings of varying AR often focuses on single flapping configurations (Hammer, Garmann, & Visbal, 2021;Zhong, Han, Moored, & Quinn, 2021;Zurman-Nasution et al., 2021b) with only a few studies related to tandem arrangements (Arranz, Flores, & Garcia-Villalba, 2020;Jurado, Arranz, Flores, & García-Villalba, 2022). A key feature of the above is the presence of tip vortices that transform the 2-D wake into a complex chain of ring-like formations (Li, Pan, Zhao, Ma, & Wang, 2018;Shao et al., 2010). ...

... Strong lift oscillations, characteristic of buffet, can be seen for the free-transition cases with a peak observed in the PSD at = 0.11 and 0.15 for cases A5M7F and A5M735F, respectively (highlighted seen here is that the turbulent buffet frequency ( = 0.13) remains approximately the same as that of laminar buffet ( = 0.15) at these conditions. It can also be inferred from the temporal variations in Fig. 3a that the time-averaged is approximately the same at a given for both free-and forced-transition cases (see Table 1 [44], more recent experiments at ONERA † and LES in [45]). Interestingly, multiple shock waves were also observed in steady inviscid calculations by [45]. ...

... In fact, the peculiarities of the trailing-edge dynamics have also been reported in other cases besides the ramp motion [15,[32][33][34][35]. Naturally, the mismatch between pitch and plunge under certain conditions resulted in questioning the validity of the effective angle-of-attack definition [32,36]. Recently, Visbal and Garmann [37] attributed the differences between pitch and plunge to the rotation-induced apparent camber effect. After subtracting this contribution from the pitching airfoil, the previous authors were able to reconcile lift and moment coefficients for periodic maneuvers. ...

... Pressure is a thermodynamic property that plays a key role in fluid mechanics. It is of utmost importance in aerodynamic load prediction [1,2,3], noise generation [4,5], flow instability and turbulence [6,7,8], and flow control [9]. The increase of time resolution in velocity field measurements during the last decade has opened the path to obtaining instantaneous pressure fields by combining experimental data with the flow governing equations [10,11]. ...

... Flow separation initiates at the leading edge following LSB bursting that concentrates into a leading-edge vortex (LEV). Aside from the tip vortices (TVs) near the wingtips, the inception of unsteady separation for the finite wings develops similarly to that observed for 2-D sections (e.g., [37,43]). By α 20.6°↑ (Fig. 2a), the LEV remains nearly spatially uniform across the span at this angle, with the exception of two features. ...

... The capstone of the current work is performing Reynolds-Averaged Navier-Stokes (RANS) simulations of a single bell-loaded configuration to both support the Euler simulation results and provide motivation for future efforts. The planform selected is a stationary AR = 8 swept wing (Λ = 30 • ) depicted in Fig. 2. The choice of this configuration is based on previous work investigating the unsteady flow-structure of a high aspect ratio swept wing undergoing dynamic stall using high-fidelity implicit Large-Eddy Simulation (ILES) [25]. The bell-shaped lift distribution is achieved on the swept wing by a combination of aerodynamic and geometric twist. ...

... Although the numerical study of a panel clamped on all sides (making the interaction inherently 3D) has also been carried out in recent years, (see Shinde et al. 2019 andBoyer et al. 2021), most of the existing numerical researches consider quasi-2D interactions with panels that have free edges at the lateral sides (as in Pasquariello et al. (2015) and Visbal (2012)). Therefore, in this study a panel with free side edges has been investigated, predicting a nominally 2D character from both the flow (at least close to the panel centerline; see Bermejo-Moreno et al. (2014) for an analysis of confinement effects) and structural perspective. ...

... The Chimera overset technique with high-order interpolation [50] transfers information between connected grids. The flow for static airfoil and constant-rate pitchup conditions was computed on the baseline (fine) grid and two additional meshes of increasing coarseness to address the effect of grid resolution: the details of which are provided in Ref. [51]. Strong agreement was found between the fine-and medium-resolution grids, demonstrated by convergence of the loads, the pressure and skin friction at the surface, and the qualitative flow structure. ...

... Dynamic stall phenomenon will seriously change the fatigue loads of turbomachinery and affect its life. In order to study the mechanism of dynamic stall, Visbal (2014) (Visbal and Garmann, 2018) (Hammer et al., 2021) employed a high-fidelity implicit large-eddy simulations approach based on high-order compact schemes analysis the onset of unsteady separation and dynamic stall vortex formation over an intermediate Reynolds number constant-rate pitching NACA0012 airfoil. They analyzed the dynamic stall process of NACA0012 airfoil in detail through the fine flow field around the airfoil, especially the boundary layer so that we could intuitively analyze and understand the change of the flow field around the airfoil in the dynamic stall process. ...