Abstract We numerically investigated two-dimensional laminar flow past a circular cylinder near a moving wall for Reynolds numbers ranging from 60–200. The gap-to-diameter ratio (G/D) between the cylinder and wall varied from 0.2–10. We studied the enhancement of the gap-induced asymmetric flow, which leads to the transition of the dominant frequency of the drag coefficient, and its association with vortical development. Harmonic analysis of the drag coefficient was performed to estimate the contributions of ω and 2ω to the periodic fluctuation of the drag coefficient, where ω is the lift force frequency. The first harmonic, which represented the primary characteristics of the pressure coefficient, was significantly more affected by the gap than the second harmonic. We found that the simultaneous combination of the harmonic components acting on the upper and lower sides of the cylinder determined the dominant frequency of the gap-induced asymmetric flow. Typical features of a gap-induced asymmetric flow are shown in the instantaneous trace of the pressure fluctuation. This revealed that the negative pressure fluctuations induced by the gap effect on the lower side were stronger than those on the upper side. This leads to a shift in the position of the zero first harmonic amplitude, ultimately resulting in a phase difference between the two sides. Finally, the dominant frequency transition of the drag coefficient occurred at smaller gaps as the Reynolds number increased.

Purpose With the emergence of a variety of communication channels on social media, employees have more opportunities to engage with external stakeholders for or against their organizational brand. In such a context, focusing on negative word-of-mouth (NWOM) as an employee’s negative discretionary brand-oriented behavior, the current study aimed to identify negative emotions that can serve as drivers for NWOM more strongly than for counterproductive workplace behavior (CWB), relying on the discrete emotion perspective. This study also aimed to examine whether employees’ perceived brand knowledge can directly diminish employees’ NWOM and CWB and attenuate the influence of negative emotions. Design/methodology/approach A questionnaire was used to gather relevant data, which were analyzed by structural equation modeling. Findings The findings showed that anger was more strongly associated with employees’ NWOM than withdrawal and that envy was more strongly associated with CWB toward individuals than employees’ NWOM. Employees’ perceived brand knowledge was negatively associated with both NWOM and CWB directly and mitigated the association of negative emotions such as anger and envy with CWB, but not with NWOM. Originality/value Based on the discrete emotion perspective, the current study explored the relative magnitude of emotional antecedents for employees’ NWOM and conventional CWB. Also, it expanded the previous findings on the positive effects of perceived brand knowledge on the positive outcomes of employees’ actions and its mitigating effects on NWOM and CWB.

Abstract We numerically investigated two-dimensional laminar flow past a circular cylinder near a moving wall for Reynolds numbers ranging from 60–200. The gap-to-diameter ratio (G/D) between the cylinder and wall varied from 0.2–10. We studied the enhancement of the gap-induced asymmetric flow, which leads to the transition of the dominant frequency of the drag coefficient, and its association with vortical development. Harmonic analysis of the drag coefficient was performed to estimate the contributions of ω and 2ω to the periodic fluctuation of the drag coefficient, where ω is the lift force frequency. The first harmonic, which represented the primary characteristics of the pressure coefficient, was significantly more affected by the gap than the second harmonic. We found that the simultaneous combination of the harmonic components acting on the upper and lower sides of the cylinder determined the dominant frequency of the gap-induced asymmetric flow. Typical features of a gap-induced asymmetric flow are shown in the instantaneous trace of the pressure fluctuation. This revealed that the negative pressure fluctuations induced by the gap effect on the lower side were stronger than those on the upper side. This leads to a shift in the position of the zero first harmonic amplitude, ultimately resulting in a phase difference between the two sides. Finally, the dominant frequency transition of the drag coefficient occurred at smaller gaps as the Reynolds number increased.

Purpose With the emergence of a variety of communication channels on social media, employees have more opportunities to engage with external stakeholders for or against their organizational brand. In such a context, focusing on negative word-of-mouth (NWOM) as an employee’s negative discretionary brand-oriented behavior, the current study aimed to identify negative emotions that can serve as drivers for NWOM more strongly than for counterproductive workplace behavior (CWB), relying on the discrete emotion perspective. This study also aimed to examine whether employees’ perceived brand knowledge can directly diminish employees’ NWOM and CWB and attenuate the influence of negative emotions. Design/methodology/approach A questionnaire was used to gather relevant data, which were analyzed by structural equation modeling. Findings The findings showed that anger was more strongly associated with employees’ NWOM than withdrawal and that envy was more strongly associated with CWB toward individuals than employees’ NWOM. Employees’ perceived brand knowledge was negatively associated with both NWOM and CWB directly and mitigated the association of negative emotions such as anger and envy with CWB, but not with NWOM. Originality/value Based on the discrete emotion perspective, the current study explored the relative magnitude of emotional antecedents for employees’ NWOM and conventional CWB. Also, it expanded the previous findings on the positive effects of perceived brand knowledge on the positive outcomes of employees’ actions and its mitigating effects on NWOM and CWB.

Free-surface wave effects on the turbulent boundary layer and wake of a surface-piercing slender body are investigated by measuring the flow and free-surface elevation around the model in three different Froude number (Fr) conditions—0.126, 0.282, and 0.400. The flow is measured by a towed underwater stereoscopic particle image velocimetry system. At the lowest Fr of 0.126, there appears no significant wave pattern, but the flow retards under the free-surface. The free-surface hinders the flow underneath, as the solid surface does. The steady and smooth free-surface wave generated at the intermediate Fr of 0.282 affects the pressure gradient on the turbulent boundary layer. The momentum thickness increases due to the adverse pressure gradient from the wave trough to the wave crest. At the highest Fr of 0.400, a strong adverse pressure gradient results in flow separation and violent wave breaking. The wave-induced separation at the high Froude number condition stimulates momentum transfer and turbulence dissipation, resulting in isotropic turbulence.

As biofouling on ship hulls can reach several millimeters in thickness, accurately predicting frictional resistance requires consideration of roughness effects beyond the scope of traditional empirical formulas developed for microscale surfaces. To address this, the complex and irregular surface geometry of biofouling was simplified by decomposing it into a series of single-wave models. Large Eddy Simulations (LES) were conducted to simulate turbulent channel flow over wavy walls, generating a comprehensive dataset of frictional resistance components. The frictional force acting on the wavy surface was defined as the effective shear stress, accounting for both viscous shear and pressure-induced forces. The distribution of friction velocity exhibited a strong correlation with the pressure component acting on the surface. The friction coefficient was found to be highest in regions characterized by large wave amplitudes and short wavelengths.

Deep-learning-based Super-Resolution (SR) methods were evaluated to reconstruct pressure fields with a high resolution from low-resolution images taken from a coarse grid simulation. In addition to a canonical SRCNN(super-resolution convolutional neural network) model, two modified models from SRCNN, adding an activation function (ReLU or Sigmoid function) to the output layer, were considered in the present study. High resolution images obtained by three models were more vivid and reliable qualitatively, compared with a conventional super-resolution method of bicubic interpolation. A quantitative comparison of statistical similarity showed that SRCNN model with Sigmoid function achieved best performance with less dependency on original resolution of input images.

A hybrid turbulence model has developed by combining a sub-grid scale model using dynamic k equation in LES with k-ω SST model of RANS equation. To ascertain potential applicability of the hybrid turbulence model, fully developed turbulent channel flows at ReSUBτ/SUB=180 have been simulated of which computational domain has a top wall with coarse cells and a bottom wall with fine cells. The streamwise mean velocity and turbulent intensity profiles showed a good agreement with DNS data when using the hybrid model rather than using a single model in k-ω SST or dynamic k equation models. Computational simulations of turbulent flows around KVLCC2 with a pre-swirl duct have been mainly performed using the hybrid turbulence model. Compared to the results obtained from RANS simulation with k-ω SST model as well as LES with dynamic k equation SGS model, turbulent wakes of the duct in the present simulation using the hybrid turbulence model were very similar to that of LES. Also, the resistances acting on hull, rudder and duct in hybrid turbulence model were similar to those in RANS simulation whereas the viscous forces acting on the hull in LES had a significant error due to coarse cells inappropriate to the sub-grid scale model.