Another real gas effect is called ionization. Ionization is a process in which electrons orbiting about the nucleus of their atom are broken out of their orbits and become individual parts of the total gas mixture. Ionization progresses gradually, as does dissociation,and has an effect similar to that of dissociation on the gas properties."

另一個(gè)真實(shí)氣體效應(yīng)稱為電離。電離是沿原子核周圍軌道飛行的電子脫離自身軌道變成整個(gè)氣體混合物中獨(dú)立成分的過程。電離過程是逐漸進(jìn)行的，就像離解過程一樣，而且對于氣體性質(zhì)的影響也與離解的類似。

Understandably,when the air in the vicinity of a vehicle in flight is dissociated or dissociated and ionized,the validity of data taken in a wind tunnel at the same Mach number without dissociation is subject to question. Because of this, a tremendous effort has been devoted to the development of facilities that provide more realistic flow conditions. Unfortunately.no facility has yet been developed in which complete duplication of the flow conditions of flight can be

obtained at the higher Mach numbers. There are three prinary reasons for this. The first is the inability of available materials to withstand the extreme temperature and pressure environments without burning or some form of erosion. The result is much contamination of the flow and a rapid destruction of tunnel components at the higher temperatures. The second is the inability to maintain the high temperatures required long enough to obtain data because of extremely high heat losses from the air due to radiation. The third reason deals with the previously described dissociation phenomenon. After the air is heated it must be expanded through a nozzle in order to achieve high velocities. In the process of expansion through the nozzle it cools very rapidly. If this cooling were to take place at a slow enough rate, all of the dissociated molecules would recombine so that the air entering the test section and approaching the model would have the same composition as atmospheric air;that is, it would be a mixture of molecules of O2 and N2. However,it develops that the rate of cooling during the expansion in any practical nozzle is too fast for the recombination to occur. The result is that the air reaching the test section will be in the dissociated state at a low temperature. This phenomenon is called "flow freezing". Flow freezing affects the Mach number and other flow parameters in the test section and results in a test medjum that may differ a great deal from the desired mixture of molecules of O2 and N2.

可以理解，當(dāng)飛行器飛行時(shí)，要是附近的空氣處于離解或既離解又電離的狀態(tài)，那么，從風(fēng)洞中相同馬赫數(shù)但未離解狀態(tài)下測得的數(shù)據(jù)是否有效，就有問題了。由于這個(gè)原因，人們已經(jīng)作了極大的努力去研制能夠提供更加接近于實(shí)際氣流條件的設(shè)備。遺憾的是，迄今尚未研制出任何可在高馬赫數(shù)下完全復(fù)現(xiàn)飛行氣流條件的設(shè)備。其主要原因有三個(gè)。第一是現(xiàn)有材料不能耐溫度極高、壓力極大的環(huán)境而不被燒壞或不受某種腐蝕。其結(jié)果是，在高溫下，氣流嚴(yán)重污染，而且風(fēng)洞部件迅速損壞。第二是不能將所需的高溫維持到足以測取數(shù)據(jù)那么長的時(shí)間，因?yàn)橛捎谳椛?，空氣中的熱損耗極大。第三個(gè)原因與前面所說的離解現(xiàn)象有關(guān)。在將空氣加熱之后，必須使其經(jīng)過噴管膨脹以便達(dá)到高速。空氣在通過噴管影脹的過程中會迅速冷卻。如果這種冷卻的速度低到足以使所有離解的分子再化合，那么，空氣進(jìn)入試驗(yàn)段到達(dá)模型時(shí)，其組成會與大氣相同，也就是說，成為氧分子O2和氮分子N2組成的混合物。然而，實(shí)際情況是，任何實(shí)際噴管里氣流膨脹時(shí)冷卻速度都很快，使分子來不及重新化合。結(jié)果到達(dá)試驗(yàn)段的空氣處于低溫離解狀態(tài)。這種現(xiàn)象稱為“氣流凍結(jié)”。氣流凍結(jié)會影響試驗(yàn)段中的馬赫數(shù)和其他氣流參數(shù)，從而有可能使試驗(yàn)介質(zhì)與預(yù)期的氧氣和氮?dú)夥肿拥幕旌衔锎蟛幌嗤?/p>

Facilities which have been developed in the process of trying to provide realistic flow conditions at high speeds and which are now used fairly extensively in high-speed testing include hotshot tunnels, plasma jets, shock tubes, shock tunnels, and light gas guns. 

在試圖提供實(shí)際高速氣流條件的過程中，發(fā)展了一批設(shè)備、目前這些設(shè)備已相當(dāng)廣泛地用于高速試驗(yàn)；它們包括熱射式風(fēng)洞、等離子體射流、激波管、激波風(fēng)洞以及輕氣體炮等。

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