Characterization of counter-rotating streamwise vortices in flat rectangular channel with one-sided wavy wall

Particle Image Velocimetry (PIV) has been used to characterize the evolution of counter-rotating streamwise vortices in a rectangular channel with one sided wavy surface. The vortices were created by a uniform set of saw-tooth carved over the leading edge of a flat plate at the entrance of a flat rectangular channel with one-sided wavy wall. PIV measurements were taken over the spanwise and streamwise planes at different locations and at Reynolds number of 2500. Two other Reynolds numbers of 2885 and 3333 have also been considered for quantification purpose. Pairs of counter-rotating streamwise vortices have been shown experimentally to be centred along the spanwise direction at the saw-tooth valley where the vorticity ωz=0. It has also been found that the vorticity ωz of the pairs of counter-rotating vortices decreases along the streamwise direction, and increases with the Reynolds number. Moreover, different quantifications of such counter-rotating vortices have been discussed such as their size, boundary layer, velocity profile and vorticity. The current study shows that the mixing due to the wall shear stress of counter-rotating streamwise vortices as well as their averaged viscous dissipation rate of kinetic energy decrease over flat and adverse pressure gradient surfaces while increasing over favourable pressure gradient surfaces. Finally, it was also demonstrated that the main direction of stretching is orientated at around 45° with the main flow direction

Visualization of pre-set vortices in boundary layer flow over wavy surface in rectangular channel

Smoke-wire flow visualization is used to study the development of pre-set counter-rotating streamwise vortices in boundary layer flow over a wavy surface in a rectangular channel. The formation of the vortices is indicated by the vortical structures on the cross-sectional plane normal to the wavy surface. To obtain uniform spanwise vortex wavelength which will result in uniform vortex size, two types of spanwise disturbances were used: a series of perturbation wires placed prior and normal to the leading edge of the wavy surface, and a jagged pattern in the form of uniform triangles cut at the leading edge. These perturbation wires and jagged pattern induce low-velocity streaks that result in the formation of counter-rotating streamwise vortices that evolve downstream to form the mushroom-like structures on the cross-sectional plane of the flow. The evolution of the most amplified disturbances can be attributed to the formation of these mushroom-like structures. It is also shown that the size of the mushroom-like structures depends on the channel entrance geometry, Reynolds number, and the channel gap. Graphical Abstract: [Figure not available: see fulltext.

Metal-Substituted Microporous Aluminophosphates

This chapter aims to present the zeotypes aluminophosphates (AlPOs) as a complementary alternative to zeolites in the isomorphic incorporation of metal ions within all-inorganic microporous frameworks as well as to discuss didactically the catalytic consequences derived from the distinctive features of both frameworks. It does not intend to be a compilation of either all or the most significant publications involving metal-substituted microporous aluminophosphates. Families of AlPOs and zeolites, which include metal ion-substituted variants, are the dominant microporous materials. Both these systems are widely used as catalysts, in particular through aliovalent metal ions substitution. Here, some general description of the synthesis procedures and characterization techniques of the MeAPOs (metal-contained aluminophosphates) is given along with catalytic properties. Next, some illustrative examples of the catalytic possibilities of MeAPOs as catalysts in the transformation of the organic molecules are given. The oxidation of the hardly activated hydrocarbons has probably been the most successful use of AlPOs doped with the divalent transition metal ions Co2+, Mn2+, and Fe2+, whose incorporation in zeolites is disfavoured. The catalytic role of these MeAPOs is rationalized based on the knowledge acquired from a combination of the most advanced characterization techniques. Finally, the importance of the high specificity of the structure-directing agents employed in the preparation of MeAPOs is discussed taking N,N-methyldicyclohexylamine in the synthesis of AFI-structured materials as a driving force. It is shown how such a high specificity could be predicted and how it can open great possibilities in the control of parameters as critical in catalysis as crystal size, inter-and intracrystalline mesoporosity, acidity, redox properties, incorporation of a great variety of heteroatom ions or final environment of the metal site (surrounding it by either P or Al)

A proposed intermittency measurement method for transitional boundary layer flows

10.1007/BF00190260Experiments in Fluids196426-428EXFL

KEGIATAN PENELITIAN DAN PENGABDIAN PADA MASYARAKAT TAHUN 1974-1977 DI UNlVERSITAS AIRLANGGA

Fungsi perguruan tinggi terkumpul dalam Tridharma perguman tinggi, yang terdiri atas tiga unsur yaitu Pendidikan. Penelioan dan Pengabdian pada Masyarakat. Ketiga dhanna Jili pada permulaan seann-akan tampak sebagai tiga unsur yang terpisah tetapi dalam perkembangan seLanjutnya ketiga Unsur ini akan makin banyak bertumpang-tindih. Tumpang-tindih ini sudah jelas terlihat di Universitas Airangga dan perkembangan seLanjutnya harus diarahkan sehingga tiga dharma pad. akhirnya ak.n bempa satu kesatuan. Dalam HKerangka Pengembangan Penelitian di Perguruan Tinggi yang dikeluarkan leh Ditjen Penti Departernen P &. K «lab tertera maksud dan tujuan pengembangan dhanna Penelitian. Dalam pembangunan negan dan bangsa Indonesia peran ilmu pengetahuan dan teknologi menjadi Makin penting, bahkan menjadi faktor penenrn apakah bangsa dan negara Indonesia dap.t berh.sil melaksanakan pemb.ngunanny. menjadikan Indonesia satu warga yang terhormat dalam lingkungan negara-negara yang sudah berkembang. Tugas Petguruan Tinggi dalam pembangunan ini antara lain mengembangkan Perguruan Tinggi menjadl tcmpat pengembangan ilmu pengetahuan. Kenyataan di Indonesia pada masa sekarang ini Wah bahwa tenaga yang mampu mengembangkan ilmu pengetahuan dan teknologi terkumpul terutama di Perguruan Tinggi dengan sa.rananya. Mengingat bahw. kunei kebemasilan pengembangan ialah ten!:a yang trampil dan mampu maka sungguh berat tugas Perguruan Tinggi dalam pembangunan ini. Hasil penelitian ini yang berupa pengembangan ilmu pengetahun dan pener.pannya perlu diam.lkan pad. masyarakat, dengan demikian basil penelitian dap.t langsung berguna untuk pembangunan. Penterjemahan dan penyampaian hasil penelitian sehingga dapat digunakan oleh masyarakat ialah inti isi dhanna Pengabdian pada Masyarakat. Garis~garis besa.mya pun sudah ditentukan oleh Ditjen Penti Depanemen P & K tetapi masih harus dicari jalan sehingga dengan pengalaman dan kemampuan yang sudah ada di Universitas Airlangga dan yang masih akan dapat dikembangkan, pengembangan dharma Pengahdian pad. Masyarakat dapat berjalan sebaik-baiknya

Selective regulation of nuclear orphan receptors 4A by adenosine receptor subtypes in human mast cells

Nuclear orphan receptors 4A (NR4A) are early responsive genes that belong to the superfamily of hormone receptors and comprise NR4A1, NR4A2 and NR4A3. They have been associated to transcriptional activation of multiple genes involved in inflammation, apoptosis and cell cycle control. Here, we establish a link between NR4As and adenosine, a paradoxical inflammatory molecule that can contribute to persistence of inflammation or mediate inflammatory shutdown. Transcriptomics screening of the human mast cell-line HMC-1 revealed a sharp induction of transcriptionally active NR4A2 and NR4A3 by the adenosine analogue NECA. The concomitant treatment of NECA and the adenosine receptor A2A (A2AAR) selective antagonist SCH-58261 exaggerated this effect, suggesting that upregulation of these factors in mast cells is mediated by other AR subtypes (A2B and A3) and that A2AAR activation counteracts NR4A2 and NR4A3 induction. In agreement with this, A2AAR-silencing amplified NR4A induction by NECA. Interestingly, a similar A2AAR modulatory effect was observed on ERK1/2 phosphorylation because A2AAR blockage exacerbated NECA-mediated phosphorylation of ERK1/2. In addition, PKC or MEK1/2 inhibition prevented ERK1/2 phosphorylation and antagonized AR-mediated induction of NR4A2 and NR4A3, suggesting the involvement of these kinases in AR to NR4A signaling. Finally, we observed that selective A2AAR activation with CGS-21680 blocked PMA-induced ERK1/2 phosphorylation and modulated the overexpression of functional nuclear orphan receptors 4A. Taken together, these results establish a novel PKC/ERK/nuclear orphan receptors 4A axis for adenosinergic signaling in mast cells, which can be modulated by A2AAR activation, not only in the context of adenosine but of other mast cell activating stimuli as well