Evaluating the applicability of a phase-averaged processing of skin-friction field measurement using an optical flow method

Lee, Chungil; Lee, Taekjin; Nonomura, Taku; Asai, Keisuke

doi:10.1007/s12650-020-00667-6

Cited by 7 publications

(2 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Zhu et al [12] provided an L-K improvement-based method and applied it into mileage calculation. Lee et al [13] measured cable elongation at break based on the improved L-K optical flow method. Interframe subtraction can test and segment a moving target according to video sport information between neighboring frame images because image information between neighboring frames from a video image contains much moving target information.…”

Section: Introductionmentioning

confidence: 99%

Study on the Automatic Basketball Shooting System Based on the Background Subtraction Method

2021

Scientific Programming

View full text Add to dashboard Cite

There are many drawbacks such as clustering, background updating, inaccurate testing results, and low anti-interference performance in traditional moving target detection theory. In our study, a background subtraction method to automatically capture the basketball shooting trajectory was used to eliminate the drawbacks of the fixed-point shooting system such as cumbersome installation and time and manpower consumption. It also can improve the accuracy and efficiency of moving target detection. We also synthetically compared to common methods including the optical flow method and interframe difference method. Results showed that the background subtraction method has better accuracy with an accuracy rate over about 90% than the interframe subtraction method (88%) and the optimal flow method (85%) and presents excellent robustness with considering variable speed and nonrigid objects. Meanwhile, the automatic detection system for basketball shooting based on background subtraction is built by coupling background subtraction with detection characteristics. The system detection speed built is further accelerated, and the image denoising is improved. The trajectory error rate is about 0.3, 0.4, and 0.5 for the background subtraction method, interframe subtraction method, and optimal flow method, respectively.

show abstract

Section: Introductionmentioning

confidence: 99%

Study on the Automatic Basketball Shooting System Based on the Background Subtraction Method

2021

Scientific Programming

View full text Add to dashboard Cite

show abstract

“…最も実用的な計測技術の一つとして, 油膜を用いた手法; オイル干渉法 7,8) , 油膜法 9,10) がある. 近年, 油膜法による計測においては, 油膜厚さの計測手法の改良によって剥離, 再付着等を含む複雑流れ場への適用が可能となるとともに 11,12) , 処理手法の改良によって非定常流れ場, 遷/超音速流れ場への適用も可能となりつつある [13][14][15][16] . 一方, オイル干渉法と油膜法を組み合わせ, 表面摩擦力を定量的に面計測する方法が提案 17) されているものの, 油膜による表面摩擦力計測は, 油膜の温度変化による計測精度の悪化が課題となる 18) .…”

unclassified

Measurement of skin friction distribution using oil film for industrial wind tunnels

Iijima

Uchiyama

Kato

2021

TVSJ

View full text Add to dashboard Cite

The quantitative skin friction distributions on a flat plate have been successfully measured in a low-speed wind tunnel combining two methods; oil film interferometry method and luminescent oil flow method. In addition, oil temperature dependency for the two methods has been eliminated by monitoring the model surface temperature with IR camera applying a polyimide tape to the aluminum surface of the plate to increase the surface emissivity. Images for two methods were corresponded to the temperature images by using 3D mapping technique. As a result, skin friction distribution corrected using the model surface temperature was improved by approximately 10% compared to that corrected using wind tunnel total temperature (T0).

show abstract

Feasibility of skin-friction field measurements in a transonic wind tunnel using a global luminescent oil film

et al. 2021

Self Cite

View full text Add to dashboard Cite

The feasibility of skin-friction field measurements using the global luminescent oil-film skin-friction field estimation method was evaluated for a challenging case of a supercritical airfoil model under transonic wind-tunnel conditions (freestream Mach number of 0.72) at a high Reynolds number (10 million, based on the model chord length). The oil-film thickness and skin-friction coefficient distributions were estimated over the airfoil model upper surface for a range of angles of attack (from $$-0.4^{\circ }$$ - 0 . 4 ∘ to $$2.0^{\circ }$$ 2 . 0 ∘ ), thus enabling the study of different boundary-layer stability situations with laminar–turbulent transition, including cases with shock-wave/boundary-layer interaction. Conventional pressure measurements on the surface and in the wake of the model as well as Schlieren flow visualizations were conducted to support the oil-film based investigations. In the laminar-flow regions, the oil-film thickness could be generally kept below the critical limit of roughness that would induce premature boundary-layer transition. The skin friction in this region could be estimated with a moderate confidence level, as confirmed for portions of the chord by the reasonable agreement with numerical data obtained via laminar boundary-layer computations. Moreover, the location of transition onset was evaluated from the skin-friction estimations with relatively low uncertainty, thus enabling the examination of the transition location evolution with varying angle of attack. The estimated locations of transition onset were shown to be in general agreement with reference transition locations measured via temperature-sensitive paint. On the other hand, the oil-film thickness in the turbulent-flow regions was larger than the height of the viscous sublayer, which led to an hydraulically rough surface with increased skin friction, as compared to the clean configuration. For this reason, quantitative skin-friction estimations were not feasible in the turbulent-flow regions. The global effects of the oil-film setup on the flow around the airfoil were evaluated from the estimations of the aerodynamic coefficients. In particular, it was shown that the presence of the specific base coat used for the application of the oil film already induced a significant increase in airfoil drag, as compared to the clean configuration, whereas a thin oil film led to negligible or small additional increases in drag. Based on the present observations, considerations for the further improvement of the global luminescent oil-film skin-friction field estimation method in transonic flow experiments at high Reynolds numbers are elucidated. Graphic abstract

show abstract

Evaluating the applicability of a phase-averaged processing of skin-friction field measurement using an optical flow method

Cited by 7 publications

References 12 publications

Study on the Automatic Basketball Shooting System Based on the Background Subtraction Method

Study on the Automatic Basketball Shooting System Based on the Background Subtraction Method

Measurement of skin friction distribution using oil film for industrial wind tunnels

Feasibility of skin-friction field measurements in a transonic wind tunnel using a global luminescent oil film

Contact Info

Product

Resources

About