On the influence of spike shape at supersonic flow past blunt bodies

Da bi se eliminsala pojava jakog udarnog talasa pri nadzvučnom opstrujavanju projektila, koja zanačajno povećava otpor pri letu krozvazduh, na njegov vrh montira se igla. U radu se daju rezultati eksperimentalnog istraživanja uticaja oblika igle na aerodinamičke koeficijente (uzgona, otpora, momenta propinjanja, kao i položaj centra pritiska) pri nadzvučnom opstrujavanju tela zaobljenog vrha. Eksperiment je izveden u aereotunelu, za jednu vrednost Mahovog i Rejnoldsovog broja, kao i za jednu vrednost napadnog ugla α = 2o. Za telo bez igle, kao i za telo sa četiri različita modela igle merene su aerodinamičke sile i momenti. U radu su predloženi kriterijumi za procenu uticaja igle zasnovani isključivo na rezultataima dobijrenim vizualizacijom strujanja. Igla najboljih karakteristika, od ispitanih konfiguracija, izabrana na osnovu izmerenih aerodinamičkih koeficijenata, uklapa se u ove kvalitativne kriterijume.In order to eliminate the appearance of a strong shock wave at a supersonic flight of a missile, which considerably increases the drag during its flight through the air, a spike is mounted on its nose. Presented paper offers the results of an experimental analysis of the influence of the spike's shape on the aerodynamic coefficients (drag, lift and pitching moment coefficient, as well as the location of the center of pressure) at supersonic flow past blunt-nosed body. The experiment was carried out in a wind tunnel, for one value of Mach and Reynolds numbers, and for one value of the angles of attack, α = 2o. For the body without spike, and with four different spike shapes, the aerodynamic forces and moment were measured. Using only the photos obtained by Schlieren visualization of the flow, the paper proposes a criterion of estimating the aerodynamic effect of the spike shape. The best spike shape from the experimental set of spikes, selected by the measurement of the aerodynamic coefficients, coincided with this qualitative criterion

On the influence of spike shape at supersonic flow past blunt bodies

Da bi se eliminsala pojava jakog udarnog talasa pri nadzvučnom opstrujavanju projektila, koja zanačajno povećava otpor pri letu krozvazduh, na njegov vrh montira se igla. U radu se daju rezultati eksperimentalnog istraživanja uticaja oblika igle na aerodinamičke koeficijente (uzgona, otpora, momenta propinjanja, kao i položaj centra pritiska) pri nadzvučnom opstrujavanju tela zaobljenog vrha. Eksperiment je izveden u aereotunelu, za jednu vrednost Mahovog i Rejnoldsovog broja, kao i za jednu vrednost napadnog ugla α = 2o. Za telo bez igle, kao i za telo sa četiri različita modela igle merene su aerodinamičke sile i momenti. U radu su predloženi kriterijumi za procenu uticaja igle zasnovani isključivo na rezultataima dobijrenim vizualizacijom strujanja. Igla najboljih karakteristika, od ispitanih konfiguracija, izabrana na osnovu izmerenih aerodinamičkih koeficijenata, uklapa se u ove kvalitativne kriterijume.In order to eliminate the appearance of a strong shock wave at a supersonic flight of a missile, which considerably increases the drag during its flight through the air, a spike is mounted on its nose. Presented paper offers the results of an experimental analysis of the influence of the spike's shape on the aerodynamic coefficients (drag, lift and pitching moment coefficient, as well as the location of the center of pressure) at supersonic flow past blunt-nosed body. The experiment was carried out in a wind tunnel, for one value of Mach and Reynolds numbers, and for one value of the angles of attack, α = 2o. For the body without spike, and with four different spike shapes, the aerodynamic forces and moment were measured. Using only the photos obtained by Schlieren visualization of the flow, the paper proposes a criterion of estimating the aerodynamic effect of the spike shape. The best spike shape from the experimental set of spikes, selected by the measurement of the aerodynamic coefficients, coincided with this qualitative criterion

Merenje prelaznih opterećenja na dva modela u aero tunelu t-38 / Measurement of transient loads on two models

Pri ispitivanju modela u "rafalnom" aerotunelu sa prekidnim dejstvom T-38, na Mahovim brojevima većim od 2, moraju se uzeti u obzir prelazne pojave koje se javljaju na početku i na kraju rada aerotunela. To su stanja kada su model i aerovaga izloženi velikim aerodinamičkim silama i momentima. Ova kombinovana opterećenja mogu oštetiti modele i aerovage, pa bi bilo potrebno unapred znati kolike se vrednosti očekuju za pojedine konfiguracije modela, kako bi se izvršio pravilan izbor aerovage i odgovarajućih materijala za izradu modela. U tu svrhu postoje dijagrami koji pružaju mogućnost procene ovih opterećenja. Dijagrami su dobijeni na osnovu ispitivanja nekoliko različitih modela na Mahovim brojevima većim od 2. U radu su prikazana merenja prelaznih opterećenja na još dva modela, a rezultati su upoređeni sa već postojećim dijagramima. / The T-38 wind tunnel is a blow down, intermittent-run type of wind tunnels. During model testing in the this type of wind tunnels, at Mach numbers higher than 2, transient loads which appear during the starting and stopping of the wind tunnel runs must be taken into consideration. These are the conditions when a model and the wind tunnel balance are exposed to large aerodynamic forces and moments. These combined loads can damage models and wind tunnel balances, and, for this reason, it is very important to determine them in advance for any particular model configuration so that an appropriate wind tunnel balance and materials for model manufacturing can be chosen. For that purpose there are graphs which give possibilities to estimate these loads. The graphs are based on experiments with a number of different models at Mach numbers higher than 2. This paper gives the measurements of transient loads on two more models and the results are compared with the already existing graphs

Merenje prelaznih opterećenja na dva modela u aero tunelu t-38 / Measurement of transient loads on two models

Pri ispitivanju modela u "rafalnom" aerotunelu sa prekidnim dejstvom T-38, na Mahovim brojevima većim od 2, moraju se uzeti u obzir prelazne pojave koje se javljaju na početku i na kraju rada aerotunela. To su stanja kada su model i aerovaga izloženi velikim aerodinamičkim silama i momentima. Ova kombinovana opterećenja mogu oštetiti modele i aerovage, pa bi bilo potrebno unapred znati kolike se vrednosti očekuju za pojedine konfiguracije modela, kako bi se izvršio pravilan izbor aerovage i odgovarajućih materijala za izradu modela. U tu svrhu postoje dijagrami koji pružaju mogućnost procene ovih opterećenja. Dijagrami su dobijeni na osnovu ispitivanja nekoliko različitih modela na Mahovim brojevima većim od 2. U radu su prikazana merenja prelaznih opterećenja na još dva modela, a rezultati su upoređeni sa već postojećim dijagramima. / The T-38 wind tunnel is a blow down, intermittent-run type of wind tunnels. During model testing in the this type of wind tunnels, at Mach numbers higher than 2, transient loads which appear during the starting and stopping of the wind tunnel runs must be taken into consideration. These are the conditions when a model and the wind tunnel balance are exposed to large aerodynamic forces and moments. These combined loads can damage models and wind tunnel balances, and, for this reason, it is very important to determine them in advance for any particular model configuration so that an appropriate wind tunnel balance and materials for model manufacturing can be chosen. For that purpose there are graphs which give possibilities to estimate these loads. The graphs are based on experiments with a number of different models at Mach numbers higher than 2. This paper gives the measurements of transient loads on two more models and the results are compared with the already existing graphs

Experimental investigation of the influence of the spike on the aerodynamic characteristics of blunt body

Strujna slika oko zaOblenog tela sa iglom zavisi od geometrijskog oblika tela i igle, kao i vrednosti Mahovog i Rejnoldsovog broja strujanja. U radu su prikazani rezultati eksperimentalnog ispitivanja modela rakete polusfernog vrha bez i sa tri igle različitog oblika. Vrednosti. Ispitivanje je obavljeno u aerotunelu za Mahov broj neporemećene struje su 1.03 i 1.88. Napadni ugao modela se menjao od –4.0˚ do 10.0˚. Vizualizacija strujanja je vršena šliren metodom i holografskom interferometrijom. Ispitivanja su pokazala da se ugradnjom igle na vrh rakete, za nadzvučna strujanja, značajno menja slika strujnog polja, a samim tim i aerodinamičke karakteristike rakete.The flow around the blunt nosed body with the spike depends of geometrical shape of the body and spike, also of Mach and Reynolds number. In this paper are presented the experimental test results of the missile model with semi spherical shaped without spike and with three different spike shapes. The test is performed in the three sonic wind tunnel for M= 1.03 i 1.88. The value of the angles of attack is between α=-4.0˚ and 10.0˚. Schlieren method and holographic interferometry are used for flow visualization. The tests show that the building of spike on the model top, for supersonic flow significantly changes the flow around model and its aerodynamically coefficients

Experimental investigation of the influence of the spike on the aerodynamic characteristics of blunt body

Strujna slika oko zaOblenog tela sa iglom zavisi od geometrijskog oblika tela i igle, kao i vrednosti Mahovog i Rejnoldsovog broja strujanja. U radu su prikazani rezultati eksperimentalnog ispitivanja modela rakete polusfernog vrha bez i sa tri igle različitog oblika. Vrednosti. Ispitivanje je obavljeno u aerotunelu za Mahov broj neporemećene struje su 1.03 i 1.88. Napadni ugao modela se menjao od –4.0˚ do 10.0˚. Vizualizacija strujanja je vršena šliren metodom i holografskom interferometrijom. Ispitivanja su pokazala da se ugradnjom igle na vrh rakete, za nadzvučna strujanja, značajno menja slika strujnog polja, a samim tim i aerodinamičke karakteristike rakete.The flow around the blunt nosed body with the spike depends of geometrical shape of the body and spike, also of Mach and Reynolds number. In this paper are presented the experimental test results of the missile model with semi spherical shaped without spike and with three different spike shapes. The test is performed in the three sonic wind tunnel for M= 1.03 i 1.88. The value of the angles of attack is between α=-4.0˚ and 10.0˚. Schlieren method and holographic interferometry are used for flow visualization. The tests show that the building of spike on the model top, for supersonic flow significantly changes the flow around model and its aerodynamically coefficients

Influence of Spike Shape at Supersonic Flow Past Blunt-Nosed Bodies

Abstract. In order to eliminate the appearance of a strong shock wave at a supersonic flight of a missile, which considerably increases the drag during its flight through the air, a spike is mounted on its nose. Presented paper offers the results of an experimental analysis of the influence of the spike's shape on the aerodynamic coefficients (drag, lift and pitching moment coefficient, as well as the location of th