| 摘要: | 2002年12月21日，復興航空GE-791貨機，因遭遇積冰問題而失事墜毀
於澎湖外海。本文針對此台灣境內首例因積冰失事之案件，參考飛行安全委
員會之失事報告，並以復興航空ATR-72為例，模擬二維外形下主翼與水平尾
翼遭遇積冰狀態之升阻力係數與力矩係數相關變化，更進一步的利用飛行力
學分析軟體探究在三維外形下積冰現象對飛機性能參數之影響。
本研究以CFD方法模擬積冰外形生成，利用對翼外形產生非結構網格，
將Navier-Stokes方程式簡化為Euler方程式並以有限體積法離散求解之，最
後以水滴軌跡方程式生成積冰之外形。考慮ATR-72機型因特有T型尾翼，水
平尾翼不受主翼之尾流場之影響，針對當時大氣環境分別模擬出光滑冰
(Glaze Ice)與透明冰(Clear Ice)兩種不同積冰於主翼及水平尾翼上作堆
積，並利用FLUENT軟體求其流場解分析其氣動力之影響。並利用飛行力學軟
體DATCOM模擬在三維外形下遭遇積冰現象下飛行性能參數。
根據計算之結果發現，在二維狀態下於翼面上積冰外形越趨不規則，其
升力係數將越趨遞減，阻力係數隨之提高；在水平尾翼上之積冰將減少其負
向升力，導致負向力矩之增加，水平尾翼氣流提前分離造成失速狀態，將使
機首產生一突然向下之俯仰力矩，對飛行安全上造成極大之威脅。在三維外
型外型處理下，因DATCOM為飛機設計之初步設計之工具，對於積冰後外型處
理有較大誤差，因此未來在這一部分有較大的改進空間，以更精確的模擬出
真實的飛行姿態。
The Trans Asia Airway flight GE-791, an ATR-72 airplane
encountered ice accretion to crash at Peng Hu Island, Taiwan, December
21, 2002, was the first ice accretion accident case ever in Taiwan. This
thesis is based on Aviation Safety Council accident report, and taking
GE791 as the case for numerically simulating aerodynamic coefficients
of main wing and horizontal tail under several two-dimensional icing
conditions.
This study uses existing CFD method to predict the ice accretion on
airfoil. First step is the generation of unstructured grid on the wing and
tail configurations. Secondly, solve Navier-Stokes equation with finite
volume method. Finally, the equation of motion for supercooled water
droplets is implemented for ice accumulation production on the airfoil
leading edge locations. Considering the ATR-72 has distinctive T-tail
shape, it is assumed that the tail will not influenced by the main wing
trailing vortices, thus the glaze ice and clear ice can be simulated under
proper atmospheric conditions. The two-dimensional iced airfoil shapes
are achieved, and the results are extended to three-dimensional and then
IV
use the flight mechanics software DATCOM to analyze the aircraft
performance behavior.
According to the above research, in two-dimensional the airfoil ice
shape is more anomalous; their lift coefficients will hastily decreasing
and drag coefficient will increase. In addition, the ice accretion
phenomenon will cause the horizontal tail to stall ahead of time. When
tail stalls, this downward force is lessened or removed, and nose of the
airplane can severely pitch down, this leads to threaten of flight safety
and is the major cause of ATR-72 accident. On the other hand the
DATCOM is an aircraft preliminary design tool, so it has error in
analyzing complicated ice shapes. There are still major rooms for
improvement in prediction of actual airplane flight performance through
this software. |
