CAJ | 학술논문

根据数值分析得到的低速风洞收缩段边界层位移厚度分布通用曲线，针对航空声学引导风洞收缩段，推导得出收缩段边界层位移厚度分布曲线，并对收缩段型面进行修正设计，给出了修正前后的型面坐标偏差，设计加工了试验件，并进行了收缩段修正前后流场的数值模拟和实验验证。数值模拟结果表明：尽管航空声学引导风洞收缩段的边界层很薄，最大位移厚度只相当于试验段水力直径的0．5％左右，但修正效果明显。对于开口和闭口试验段流场，在收缩段型面设计时考虑粘性影响，进行边界层修正，均可显著降低试验段的动压场系数；减小气流偏角，提高试验段流场品质，有利于风洞部段的精细化设计。收缩段型面出口由于逆压梯度的存在，壁面速度过冲，气流均匀性较差，但进入平直段后，动压不均匀度及气流偏角迅速下降，因此收缩段后16．7％长度的平直段对于改善试验段流场品质很关键。在航空声学引导风洞上，采用移测架、皮托管和热线风速仪进行了修正前后收缩段、试验段动压和速度值测量，测量结果也验证了边界层修正的效果，而且实测的边界层位移厚度与理论推导值吻合。根据测量的收缩段内和出口的边界层速度分布，计算边界层位移厚度、动量损失厚度和形状因子，并据此判定，航空声学引导风洞收缩段内的边界层流动保持层流状态，未发生层流到湍流的转捩。
근거수치분석득도적저속풍동수축단변계층위이후도분포통용곡선，침대항공성학인도풍동수축단，추도득출수축단변계층위이후도분포곡선，병대수축단형면진행수정설계，급출료수정전후적형면좌표편차，설계가공료시험건，병진행료수축단수정전후류장적수치모의화실험험증。수치모의결과표명：진관항공성학인도풍동수축단적변계층흔박，최대위이후도지상당우시험단수력직경적0．5％좌우，단수정효과명현。대우개구화폐구시험단류장，재수축단형면설계시고필점성영향，진행변계층수정，균가현저강저시험단적동압장계수；감소기류편각，제고시험단류장품질，유리우풍동부단적정세화설계。수축단형면출구유우역압제도적존재，벽면속도과충，기류균균성교차，단진입평직단후，동압불균균도급기류편각신속하강，인차수축단후16．7％장도적평직단대우개선시험단류장품질흔관건。재항공성학인도풍동상，채용이측가、피탁관화열선풍속의진행료수정전후수축단、시험단동압화속도치측량，측량결과야험증료변계층수정적효과，이차실측적변계층위이후도여이론추도치문합。근거측량적수축단내화출구적변계층속도분포，계산변계층위이후도、동량손실후도화형상인자，병거차판정，항공성학인도풍동수축단내적변계층류동보지층류상태，미발생층류도단류적전렬。
On the basis of the master curve of boundary layer displacement thickness for low speed wind tunnel contraction obtained from numerical research,the distribution of the displace-ment thicknessδ* for the pilot aeroacoustic wind tunnel(PAWT)’s contraction is derived.Ac-cordingly,we redesigned the contraction contour,gave the deviation after correction,fabricated the test article,and conducted the numerical simulation and experimental study.The numerical results show that,although the boundary layer of the contraction was very thin and the maxi-mumδ* was only 0 .5% or so of the test section hydraulic diameter,the correction effect was re-markable.After the correction,for both open and closed test sections,the dynamic pressure non-uniformity was reduced,the flow-deviation angle decreased,and the flow field quality was im-proved.At the contraction exit,the near wall velocity was overshoot due to the reverse pressure gradient.But after entering the straightness section,the dynamic pressure non-uniformity and the flow angle decreased sharply.After the contraction,there is a straight section whose length is 1 6 .7% of contraction,which is very helpful for improving the flowfield quality.Using mova-ble measuring device,pitot tube and hotwire anemometer,we measured the dynamic pressure and velocity before and after the correction.The measuredδ* coincides with the theoreticalδ*, and the effect of boundary correction is verified experimentally.Based on the measured velocity distribution,it can be inferred that the boundary layer in the contraction of PAWT is laminar, without transition from laminar to turbulent flow.