Drag reduction by means of dimpled surfaces in turbulent boundary layers

Nesselrooij, Michiel van; Veldhuis, L.L.M.; Oudheusden, B.W. van; Schrijer, F.F.J.

doi:10.1007/s00348-016-2230-9

Cited by 55 publications

(70 citation statements)

References 22 publications

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“…The purpose of the actuators is to reduce or eliminate flow separation [9], reduce turbulent drag [10] and/or reduce noise [11]. Low-pressure turbines (LPTs) in particular are exposed to flow separation due to increased blade loading.…”

Section: Active Methodsmentioning

confidence: 99%

“…For actuators using periodic excitation (pulsed, unsteady operation), the excitation parameters, i.e., frequency, amplitude, and duty cycle, are important [12]. The operation of the actuators is based on introducing additional momentum in the near-wall flow [10,13]. The momentum addition is evaluated using the momentum coefficient, which is the ratio of additional momentum to the main flow momentum.…”

Section: Active Methodsmentioning

confidence: 99%

“…They show that drag and total pressure losses can effectively be reduced, but according to Quadrio and Ricco [14], the maximum net energy saving is only 7.3% for the actuator which could reduce drag by 44.7% due to the energy used to control the actuator. In addition to the required energy input, actuators introduce additional weight and complexity into the controlled system [10]. For example, the configuration of a pulsating jet [12] is highly complicated, and therefore, it is used mainly in the wings of air vehicles that have a long chord length.…”

Section: Active Methodsmentioning

confidence: 99%

“…Year Application Reynolds Number β = δ * τ w,0 dp dx Effect on Drag [97] 2016 Transportation, medical, industry 4180 0 −11.6% [98] 2016 Transportation, industry 4200 0 −3.9% [108] The drag reduction performance of riblets is higher at low Reynolds numbers than at high Reynolds numbers [115,116] and ice, fouling, and wearing weakens the drag reduction capability of riblets [10].…”

Section: Refmentioning

confidence: 99%

“…Dimples are not as prone to fouling and wearing as riblets [10]; however, they cause additional drag [74]. The smaller the vortex generator, the lower the additional drag, but at low Reynolds numbers, a small vortex generator might not be sufficient to induce reattachment [74].…”

Section: Turbulence and Vortex Generators (Classification: Passive Gmentioning

confidence: 99%

See 4 more Smart Citations

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

Tiainen

Grönman

Jaatinen-Värri

et al. 2017

IJTPP

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Abstract:The decrease in the performance of centrifugal compressors operating at low Reynolds numbers (e.g., unmanned aerial vehicles at high altitudes or small turbomachines) can reach 10% due to increased friction. The purposes of this review are to represent the state-of-the-art of the active and passive flow control methods used to improve performance and/or widen the operating range in numerous engineering applications, and to investigate their applicability in low-Reynolds-number centrifugal compressors. The applicable method should increase performance by reducing drag, increasing blade loading, or reducing tip leakage. Based on the aerodynamic and structural demands, passive methods like riblets, squealers, winglets and grooves could be beneficial; however, the drawbacks of these approaches are that their performance depends on the operating conditions and the effect might be negative at higher Reynolds numbers. The flow control method, which would reduce the boundary layer thickness and reduce wake, could have a beneficial impact on the performance of a low-Reynolds-number compressor in the entire operating range, but none of the methods represented in this review fully fulfil this objective.

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Section: Active Methodsmentioning

confidence: 99%

Section: Active Methodsmentioning

confidence: 99%

Section: Active Methodsmentioning

confidence: 99%

Section: Refmentioning

confidence: 99%

Section: Turbulence and Vortex Generators (Classification: Passive Gmentioning

confidence: 99%

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Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

Tiainen

Grönman

Jaatinen-Värri

et al. 2017

IJTPP

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A review on the use of passive flow control devices as performance enhancement of lift‐type vertical axis wind turbines

Syawitri

Yao

et al. 2022

WIREs Energy & Environment

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This article provides a comprehensive review about passive flow control devices (PFCDs) implemented in lift‐type vertical axis wind turbine (LVAWT), focusing on the underlying flow physics mechanisms and to what extents they can improve the LVAWT performance. In addition, some novel concepts that can be potentially implemented in future are also presented. Based on literature review, it is observed that PFCDs can enhance the power generation of LVAWT up to 172.73% compared with a clean LVAWT. However, this significant improvement still needs to be evaluated carefully by considering the economic feasibility aspect, because PCFDs can increase the design complexity, weight penalty and manufacturing cost of LVAWT. Furthermore, it is essential to design and evaluate the effectiveness of PFCDs using a full VAWT configuration by considering the blade rotating effects and blade‐to‐blade interactions. Finally, evaluation of PFCDs needs to be performed at all ranges of tip speed ratios (TSRs) operation conditions, as there are clear evidences on the correlation between LVAWT performance and different range of TSRs. This article is categorized under: Sustainable Energy > Wind Energy

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Pressure loss and heat transfer characteristics in a dimpled channel with crescent-shaped protrusion

Jeong

Park

2021

Heat Mass Transfer

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Drag reduction by means of dimpled surfaces in turbulent boundary layers

Cited by 55 publications

References 22 publications

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

A review on the use of passive flow control devices as performance enhancement of lift‐type vertical axis wind turbines

Pressure loss and heat transfer characteristics in a dimpled channel with crescent-shaped protrusion

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