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Experimental Study on the Aerodynami...

Mok, Kwan Pui,

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Experimental Study on the Aerodynamics of Windsurfing Sails /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Experimental Study on the Aerodynamics of Windsurfing Sails // Kwan Pui Mok.
作者:	Mok, Kwan Pui,
面頁冊數:	1 electronic resource (207 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-06, Section: B.
Contained By:	Dissertations Abstracts International86-06B.
標題:	Reynolds number. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31810329
ISBN:	9798346823063

Experimental Study on the Aerodynamics of Windsurfing Sails /
Mok, Kwan Pui,

Experimental Study on the Aerodynamics of Windsurfing Sails /Kwan Pui Mok. - 1 electronic resource (207 pages)

Source: Dissertations Abstracts International, Volume: 86-06, Section: B.

The sail is the primary source of propulsion in windsurfing, making it crucial to understand its aerodynamics for optimal performance. The thesis research explores the unique aerodynamic characteristics of steady sailing and sail pumping through wind tunnel experiments.The study on steady sailing utilised a scaled-down sail model to investigate the effect of the unique geometry of a windsurfing sail on aerodynamics, where the aerodynamic force, rolling moment, surface flow feature and wake total pressure are revealed. The sail was investigated under different Reynolds numbers, angles of attack, and the unique operational angles in windsurfing - the rig-back angles. This study provides insights into sail shape optimisation and experimental scaling considerations in steady sailing conditions.Evaluating the performance of windsurfing sails goes beyond aerodynamic aspects and involves mechanical considerations. This study introduces a novel operational performance analysis framework that integrates aerodynamics, sailing kinematics, and mechanical constraints. The study considers the sailor's maximum righting moment threshold when considering the maximum sail's driving force. The rolling moment limits the maximum sail's driving force, particularly when sailing upwind at high true wind speeds and sailing speeds. The study suggests that higher rig-back angles can be beneficial when the maximum driving force is restricted by the moment threshold. In these conditions, reducing sail rolling moment from a higher rig-back angle can offset the potential reduction in lift-to-drag ratio.This research also delves into the unsteady aerodynamics of a pumping sail. The study is simplified with a finite rigid wing sail with NACA 0012 cross-sectional aero foils and an aspect ratio of 3.5. The prescribed motion involves a single angular oscillatory motion parallel to the sail's chord, where the sail's motion is both parallel and perpendicular to the flow at non-zero angles of attack. A novel experimental test rig was developed. The study investigates the time-averaged and phase-averaged aerodynamic force, aerodynamic power input, and phase averaged flow vorticity. The investigation was conducted at different mean angles of attack, pump amplitudes and reduced frequencies. The study finds that the increase in driving force from sail pumping is primarily due to the increase in time-averaged lift attributed to the leading edge vortex. In general, higher leading edge vortex vorticity can be observed at higher reduced frequencies, enhancing lift and driving force. However, as reduced frequency increases further, the sail could impinge on the leading edge vortex before convicting downstream, resulting in a reduction in vorticity, thus, leading to a reduction of lift and driving force enhancement. Consequently, an optimum reduced frequency exists for maximizing lift and driving force.A novel evaluation metric is introduced to offer insights into athletes' effort and power demands during sail pumping. The study investigates two criteria of sail pumping: maximum efficiency and maximum efficacy. The optimized pumping amplitude and reduced frequency vary for each criterion, yet the optimized mean angle of attack remains consistent. Overall, this study provides insights into the aerodynamics of an oscillating sail and offers guidance into the optimizing strategy of windsurfing pumping.

English

ISBN: 9798346823063Subjects--Topical Terms:

3681436
Reynolds number.
Subjects--Index Terms:

Optimal performance

Experimental Study on the Aerodynamics of Windsurfing Sails /
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520 $a The sail is the primary source of propulsion in windsurfing, making it crucial to understand its aerodynamics for optimal performance. The thesis research explores the unique aerodynamic characteristics of steady sailing and sail pumping through wind tunnel experiments.The study on steady sailing utilised a scaled-down sail model to investigate the effect of the unique geometry of a windsurfing sail on aerodynamics, where the aerodynamic force, rolling moment, surface flow feature and wake total pressure are revealed. The sail was investigated under different Reynolds numbers, angles of attack, and the unique operational angles in windsurfing - the rig-back angles. This study provides insights into sail shape optimisation and experimental scaling considerations in steady sailing conditions.Evaluating the performance of windsurfing sails goes beyond aerodynamic aspects and involves mechanical considerations. This study introduces a novel operational performance analysis framework that integrates aerodynamics, sailing kinematics, and mechanical constraints. The study considers the sailor's maximum righting moment threshold when considering the maximum sail's driving force. The rolling moment limits the maximum sail's driving force, particularly when sailing upwind at high true wind speeds and sailing speeds. The study suggests that higher rig-back angles can be beneficial when the maximum driving force is restricted by the moment threshold. In these conditions, reducing sail rolling moment from a higher rig-back angle can offset the potential reduction in lift-to-drag ratio.This research also delves into the unsteady aerodynamics of a pumping sail. The study is simplified with a finite rigid wing sail with NACA 0012 cross-sectional aero foils and an aspect ratio of 3.5. The prescribed motion involves a single angular oscillatory motion parallel to the sail's chord, where the sail's motion is both parallel and perpendicular to the flow at non-zero angles of attack. A novel experimental test rig was developed. The study investigates the time-averaged and phase-averaged aerodynamic force, aerodynamic power input, and phase averaged flow vorticity. The investigation was conducted at different mean angles of attack, pump amplitudes and reduced frequencies. The study finds that the increase in driving force from sail pumping is primarily due to the increase in time-averaged lift attributed to the leading edge vortex. In general, higher leading edge vortex vorticity can be observed at higher reduced frequencies, enhancing lift and driving force. However, as reduced frequency increases further, the sail could impinge on the leading edge vortex before convicting downstream, resulting in a reduction in vorticity, thus, leading to a reduction of lift and driving force enhancement. Consequently, an optimum reduced frequency exists for maximizing lift and driving force.A novel evaluation metric is introduced to offer insights into athletes' effort and power demands during sail pumping. The study investigates two criteria of sail pumping: maximum efficiency and maximum efficacy. The optimized pumping amplitude and reduced frequency vary for each criterion, yet the optimized mean angle of attack remains consistent. Overall, this study provides insights into the aerodynamics of an oscillating sail and offers guidance into the optimizing strategy of windsurfing pumping.
546 $a English
590 $a School code: 1223
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650 4 $a Aerodynamics. $3 532569
650 4 $a Sea level. $3 544062
650 4 $a Water measurement. $3 3830156
650 4 $a Aerospace engineering. $3 1002622
650 4 $a Mechanical engineering. $3 649730
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653 $a Aerodynamics
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720 1 $a Zhou, Peng $e degree supervisor.
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