Geri Dön

Roughness induced transition

Başlık çevirisi mevcut değil.

PDF İndir

  1. Tez No: 540541
  2. Yazar: FAHRETTİN GÖKHAN ERGİN
  3. Danışmanlar: Dr. EDWARD B. WHITE
  4. Tez Türü: Doktora
  5. Konular: Astronomi ve Uzay Bilimleri, Makine Mühendisliği, Astronomy and Space Sciences, Mechanical Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 2005
  8. Dil: İngilizce
  9. Üniversite: Case Western Reserve University
  10. Enstitü: Yurtdışı Enstitü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 151

Özet

Özet yok.

Özet (Çeviri)

Surface roughness has numerous different effects on boundary layer stability. For roughness amplitudes lower than a critical level, the velocity disturbances roughness creates in laminar boundary layers experience a transient algebraic growth followed by exponential decay without leading to transition. When the critical level is exceeded unsteady disturbances are amplied and the ow rapidly transitions to turbulence. Whether the ow remains laminar or becomes turbulent is solely determined by the receptivity of the initial disturbance. Two experiments are performed that address two fundamental problems related to roughness induced disturbances. One examines the disturbances produced by subcritical elements. The other identies the instability mechanism responsible for breakdown in the wake of supercritical roughness elements. For subcritical conditions, multiple component velocity measurements are obtained in a at plate boundary layer in the wake of an array of subcritical cylindrical elements. These data reveal the topology of the steady horseshoe vortex that exists in the wake of roughness elements and leads to transient growth of streamwise and spanwise velocity disturbances. A theoretical technique that quanties the receptivity of velocity disturbances to surface roughness requires the complete velocity eld as input and the data obtained here are suitable for this purpose. For supercritical conditions, velocity measurements are obtained above and below the critical roughness height Reynolds number, Rek. The steady disturbance eld reveals local shear layers in the wall-normal and spanwise directions and the unsteady disturbance led reveals evidence of hairpin vortices observed in ow visualization studies. The locations of maximum uctuation intensity correspond to the locations of local inection points of the steady velocity eld suggesting that the uctuations result from a Kelvin–Helmholz-type instability. Rapid transition takes place at Rek = 334 but not below this value. The disturbances' energy growth rates indicate that the transition scenario can be understood as a competition between the unsteady disturbances' growth and the rapid relaxation of the steady ow that tends to stabilize these disturbances.

Benzer Tezler

  1. Tez No

    784097

    Boundary layer transition over rotating disks

    Dönen diskler üzerinde sınır tabaka geçişi

    MUSA ÖZKAN

    Doktora

    İngilizce

    İngilizce

    2016

    Makine MühendisliğiUniversity of Warwick

    Makine Mühendisliği Ana Bilim Dalı

    PROF. DR. PETER THOMAS

  2. Tez No

    334722

    Poli(etilen-alt-tetrafloroetilen) (ETFE) ardışık kopolimer filmine RAFT yöntemi ve radyasyon kullanılarak stiren aşılanması ve yakıt pili membranı hazırlanması

    Radiation induced, RAFT mediated grafting of styrene onto ETFE (poly(ethylene-alt-tatrafluoroethylene) alternating copolymer film and preparation of fuel cell membrane

    GÖKÇE ÇELİK

    Doktora

    Türkçe

    Türkçe

    2013

    Polimer Bilim ve TeknolojisiHacettepe Üniversitesi

    Kimya Ana Bilim Dalı

    PROF. OLGUN GÜVEN

  3. Tez No

    467187

    Numerical and experimental investigation of boundary layer transition with active and passive flow control methods

    Sınır tabaka geçişinin aktif ve pasif akış kontrol yöntemleriyle sayısal ve deneysel incelenmesi

    ABDUSSAMET SUBAŞI

    Doktora

    İngilizce

    İngilizce

    2017

    Makine Mühendisliğiİstanbul Teknik Üniversitesi

    Makine Mühendisliği Ana Bilim Dalı

    PROF. DR. HASAN GÜNEŞ

  4. Tez No

    413253

    Characterization and antimicrobial properties of multiple layer silk fibroin/hyaluronic acid film on cocrmo alloy

    Cocrmo alaşımında çoklu tabakalı ipek fibroin/hyaluronik asit filminin karakterizasyonu ve antimikrobiyal özellikleri

    PINAR ARPAÇAY

    Yüksek Lisans

    İngilizce

    İngilizce

    2013

    KimyaGediz Üniversitesi

    Nanoteknoloji ve İleri Malzemeler Ana Bilim Dalı

    YRD. DOÇ. DR. UĞUR TÜRKAN

    PROF. DR. OĞUZ BAYRAKTAR

  5. Tez No

    898345

    Poli (bütilenadipat-ko-tereftalat) (PBAT)-bazlı nanotopografik fibröz doku iskelelerinin üretimi ve hücresel davranışların incelenmesi

    Production of poly (Buthyleneadipate-co-terephthalate) (PBAT)-based nanotopographic fibrous tissue scaffolds and investigation of cellular behaviors

    ZEYNEP İLHAN

    Doktora

    Türkçe

    Türkçe

    2024

    BiyomühendislikHacettepe Üniversitesi

    Biyomühendislik Ana Bilim Dalı

    PROF. DR. MENEMŞE GÜMÜŞDERELİOĞLU

Geri Dön