Effect of Blade Leading and Trailing Edge Configurations on the Performance of a Micro Tubular Propeller Turbine Using Response Surface Methodology

With the recent rise in importance of environmental issues, research on micro hydropower, a kind of renewable energy source, is being actively conducted. In this study, a micro tubular propeller turbine was selected for study of micro hydropower in pipes. Numerical analysis was conducted to evaluate the performance. Response surface methodology using design of experiments was performed to efficiently investigate the effect of the blade leading and trailing edge elliptic aspect ratios on the performance. The trailing edge configuration was found to be more related to the performance, because of the drastic pressure variation due to the stagnation point formed, regardless of the leading edge configuration. To improve the performance, a NACA airfoil was introduced. The results show that the flow became more stable than the reference model, and the efficiency was increased by 2.44%.

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Degradation of trans-ferulic acid in aqueous solution by a water falling film DBD reactor: Degradation performance, response surface methodology, reactive species analysis and toxicity evaluation

Separation and Purification Technology ◽

10.1016/j.seppur.2019.116226 ◽

2020 ◽

Vol 235 ◽

pp. 116226 ◽

Cited By ~ 2

Author(s):

Jingyu Ren ◽

Jie Li ◽

Nan Jiang ◽

Kefeng Shang ◽

Na Lu ◽

...

Keyword(s):

Aqueous Solution ◽

Response Surface Methodology ◽

Ferulic Acid ◽

Response Surface ◽

Reactive Species ◽

Falling Film ◽

Toxicity Evaluation ◽

Species Analysis ◽

Performance Response ◽

Dbd Reactor

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Linear stability of the steady flow past rectangular cylinders

Journal of Fluid Mechanics ◽

10.1017/jfm.2021.819 ◽

2021 ◽

Vol 929 ◽

Author(s):

A. Chiarini ◽

M. Quadrio ◽

F. Auteri

Keyword(s):

Aspect Ratio ◽

Critical Reynolds Number ◽

Leading Edge ◽

Curvature Radius ◽

Trailing Edge ◽

Aspect Ratios ◽

A Value ◽

Flow Past ◽

Rectangular Cylinders ◽

Primary Instability

The primary instability of the flow past rectangular cylinders is studied to comprehensively describe the influence of the aspect ratio $AR$ and of rounding the leading- and/or trailing-edge corners. Aspect ratios ranging between $0.25$ and $30$ are considered. We show that the critical Reynolds number ( $\textit {Re}_c$ ) corresponding to the primary instability increases with the aspect ratio, starting from $\textit {Re}_c \approx 34.8$ for $AR=0.25$ to a value of $\textit {Re}_c \approx 140$ for $AR = 30$ . The unstable mode and its dependence on the aspect ratio are described. We find that positioning a small circular cylinder in the flow modifies the instability in a way strongly depending on the aspect ratio. The rounded corners affect the primary instability in a way that depends on both the aspect ratio and the curvature radius. For small $AR$ , rounding the leading-edge corners has always a stabilising effect, whereas rounding the trailing-edge corners is destabilising, although for large curvature radii only. For intermediate $AR$ , instead, rounding the leading-edge corners has a stabilising effect limited to small curvature radii only, while for $AR \geqslant 5$ it has always a destabilising effect. In contrast, for $AR \geqslant 2$ rounding the trailing-edge corners consistently increases $\textit {Re}_c$ . Interestingly, when all the corners are rounded, the flow becomes more stable, at all aspect ratios. An explanation for the stabilising and destabilising effect of the rounded corners is provided.

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On the frequency selection mechanism of the low-Re flow around rectangular cylinders

Journal of Fluid Mechanics ◽

10.1017/jfm.2021.1027 ◽

2022 ◽

Vol 933 ◽

Author(s):

A. Chiarini ◽

M. Quadrio ◽

F. Auteri

Keyword(s):

Aspect Ratio ◽

Strouhal Number ◽

Leading Edge ◽

Stream Velocity ◽

Frequency Locking ◽

Trailing Edge ◽

Aspect Ratios ◽

Nonlinear Simulations ◽

Edge Vortex ◽

Rectangular Cylinders

In the flow past elongated rectangular cylinders at moderate Reynolds numbers, vortices shedding from the leading- and trailing-edge corners are frequency locked by the impinging leading-edge vortex instability. The present work investigates how the chord-based Strouhal number varies with the aspect ratio of the cylinder at a Reynolds number (based on the cylinder thickness and the free-stream velocity) of $Re=400$ , i.e. when locking is strong. Several two-dimensional, nonlinear simulations are run for rectangular and D-shaped cylinders, with the aspect ratio ranging from $1$ to $11$ , and a global linear stability analysis of the flow is performed. The shedding frequency observed in the nonlinear simulations is predicted fairly well by the eigenfrequency of the leading eigenmode. The inspection of the structural sensitivity confirms the central role of the trailing-edge vortex shedding in the frequency locking, as already assumed by other authors. Surprisingly, however, the stepwise increase of the Strouhal number with the aspect ratio reported by several previous works is not fully reproduced. Indeed, with increasing aspect ratio, two distinct flow behaviours are observed, associated with two flow configurations where the interaction between the leading- and trailing-edge vortices is different. These two configurations are fully characterised, and the mechanism of selection of the flow configuration is discussed. Lastly, for aspect ratios close to the jump between two consecutive shedding modes, the Strouhal number is found to present hysteresis, implying the existence of multiple stable configurations. Continuing the lower shedding-mode branch by increasing the aspect ratio, we found that the periodic configuration loses stability via a Neimark–Sacker bifurcation leading to different Arnold tongues. This hysteresis can explain, at least partially, the significant scatter of existing experimental and numerical data.

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