Laminar iyo socodka qasan. gumaysiga ee socodka dareeraha

Waxbarashada sifooyinka dareerayaasha iyo gaasaska socodka waa mid aad u muhiim ah, waayo, warshadaha iyo danabka dadweynaha. The laminar iyo saamaynta socodka qasan on heerka gaadiidka biyaha, saliid, dhuumaha gaaska dabiiciga ah ujeedooyin kala duwan, oo saameyn ku soo koobin kale. Dhibaatooyinkaas samayn hydrodynamics sayniska.

kala soocidda

In deegaanka sayniska ee gumaysiga socodka dareeraha iyo gaasaska kala qaybsan yihiin laba fasal oo aad u kala duwan:

• laminar (inkjet);
• qasan.

Sidoo kale kala saaro marxaladda KMG ah. Waana mid ka, erayga "dareere" waxay leedahay macne ballaaran, waxay noqon kartaa incompressible (dareere ah run ahaantii waa), a compressible (gaaska), tabinta, iwm ...

taariikhda kiiska

Mendeleev kale in 1880 fikradda ah jiritaanka laba gumaysiga socodka soo horjeeda ayaa waxaa ka muujiyeen. Wixii faahfaahin dheeraad ah oo ku saabsan arrintan baaritaan jirka ah British iyo injineer Osborne Reynolds kuwaas oo dhamaystay waxbarasho ee 1883kii. First, ficil ahaan, kadibna la isticmaalayo qaaciidooyinka waxaa la helay in heerka socodka yar ee gaadiidka dareere foomka laminar noqonayaa: layers (socodka walxaha) waxaa ku dhowaad ma qas iyo guurto waddooyin isku midka ah. Si kastaba ha ahaatee, ka dib markii qiimaha gaar ah oo muhiim ah (xaaladaha kala duwan waa kala duwan), shuruudaha socodka dareeraha ah horyaalka tirada Reynolds waa la beddelaa, socodka jet uu noqdo Uubo qasan - i.e., qasan. Sida ka leexatay, oo xuduudaheedu waa kuwan ilaa xad soo jireenka ah iyo gaasaska.

La taaban karo Ingiriisi xisaabaha saynisyahan muujisay in dhaqanka, tus, biyaha, waa si sare ugu xiran qaabka iyo dhinacyada taangiga (tuubooyinka, channels, qalintaanka, iwm), taas oo wuxuu la barwaaqaysan. tuubooyinka ayaa isagoo ka qeyb wareeg ah (tusaale ahaan loo isticmaalaa kordhaya dhuumaha cadaadis), ay Reynolds tirada - formula ee gobolka muhiimka ah waxaa lagu tilmaamay sida soo socota: Re = 2300. Wixii socodka channels furan tirada Reynolds waa more: Re = 900. Wixii qiimaha yar ee Re yahay habsami leh, at waaweyn - qasan.

socodka laminar

Si ka duwan qasan socodka laminar waa dabeecadda iyo jihada oo biyo ah (gas) qubanayo. Waxay guurto layers oo aan la isku qasin oo aan pulsations. In si kale loo dhigo, dhaqdhaqaaqa qaadataa meel isku aan ka bootin goosgoos jihada cadaadiska iyo xawaaraha.

socodka dheecaan Laminar waxaa la aasaasay, tusaale ahaan, in cidhiidhi ah xididdada dhiigga waxyaabaha nool, qalintaanka dhirta iyo xaaladaha u dhigma, ee hadda ah oo cabitaanno ah mid aad u viscous (saliidda shidaalka iyada oo dhuumaha). Si aad u arki socodka jet waxaa ku filan inaad daaha ka yar tuubada ah - biyaha aamusnaan duuli doona, si siman, iyada oo aan la isku qasin. Haddii wareejin qasabad ilaa dhammaadka, cadaadis nidaamka kici doonaa oo u socodka noqon doonaa qasan.

socodka qasan

Si ka duwan laminar ah, kuna waari dhexdeeda qayb deriska guurto waddooyin ku ool ah isku midka ah, socodka qasan ee dareeraha waa dabeecadda Fasaadi. Haddii aan u isticmaalno hab Lagrange ah, ee trajectories ee qayb ka ah sharci darro ah u ekaan karaan iyo dhaqmaan arrin filanayn. Dhaqdhaqaaqa oo cabitaanno ah iyo gaasas ku hoos jira xaalad kuwaas oo had iyo jeer transient, la koobin kuwaas nonstationarities yeelan karaan kala duwan oo aad u ballaaran.

Sida socodka gaaska laminar galay baxa nidaam qasan, lagala socon karo by tusaale ahaan wisps qiiqa sigaarka gubanaya ah in weli hawada. Markii hore, qayb ka guurto Waddooyinkiisa ku dhowaad isku midka ah isbeddelin waqti. Smoke u muuqataa go'an. Markaas barta qaar ka mid ah oo dhan lama filaan ah waxaa jira eddies weyn in guuraan gabi ahaanba kala sooc lahayn. vortices Kuwani jabsada galay kuwa yaryar - xitaa ka yar iyo wixii la mid ah. In dhamaadka, shiidaa sigaar keegag leh hawada ku xeeran.

wareegyada qas

Tusaalaha kor ku xusan yahay buugga a, iyo ka-galku uu culumadu sameeyey gabagabadii soo socda:

1. Laminar iyo socodka qasan yihiin probabilistic ee dabiiciga ah, kala guurka oo ka mid ah hab kale ku ma aha in booska saxda ahaa, iyo in si cadaalad ah loo aabo yeelin, meel random.
2. First, waxaa jira vortices badan oo kuwa ka badan size ee wisps qiiq ah. Dhaqdhaqaaqa noqdo maha oo si xoog leh anisotropic. qulqulka Large noqon deganayn oo jabsada yar oo yar yar. Sidaas darteed, waxaa jira madaxda ah eddies. tamarta ee dhaqdhaqaaqa waxaa loo wareejiyey ka weyn in yar, iyo dhamaadka ee habka this baaba'aa - dhereg tamarta dhacdaa qolfo yar.
3. socodka qasan yahay goosgoos: Uubo gaar ah waxay noqon kartaa in gebi ahaanba random, meel aan la saadaalin karin.
4. Dhexgalo qiiqa leh hawada daarmayaay'e ayaan loo qaadan Karin meel ka yar socodka laminar, iyo in qasan - waa mid aad u xoog ah.
5. In kasta oo xaqiiqda ah in shuruudaha soohdintu waa taagan, qas laftiisa ayaa transient a fahmayaan ee dabiiciga ah - cabbir kasta oo gaas-firfircoon beddesho muddo kadib.

Waxaa jira guri kale muhiim ah oo qas: waxaa had iyo jeer waa saddex-geesood ah. Xitaa haddii aan tixgelin doonna socodka hal dhinac-cabbir ah in biibiile ama lakabka xuduud laba dhinac-cabbir weli mooshin ah eddies qasan dhacaan ee jiho oo ka mid ah saddex duwo faasas.

Reynolds lambarka: caanaha

guurka ka laminar inay qas gartaa waxa loogu yeero tirada Reynolds muhiim ah:

_{Re Cr = (/ μ ρuL)} Cr,

halkaas oo ρ - il mugga, u - heerka socodka dabeecadda; L - qulquli size sifo, μ - Wehliyaha ah ee ku nafwaayay firfircoon, Cr - for by tuubo la wareeg iskutallaabta qaybta.

Tusaale ahaan, waayo socodka leh u xawaare ee L biibiile waxaa loo isticmaalaa sida dhexroor biibiile. Osborne Reynolds muujisay in haddii ay taasi ku, 2300 Cr <20000. Faafidda waa mid aad u weyn, ku dhowaad amar of magnitude.

Natiijada A la mid ah waa la helay ee lakabka xuduud on xabbad canjeero ah. Cabbirka sifo loo qaato sida fogaanta Geesta hore ee ahaa wasladdii khafiifka, ka dibna 3 × ¹⁰ May Cr <4 × ¹⁰ April. Haddii L waxaa lagu qeexaa sida dhumucda lakabka xuduud, ee 2700 Cr <9000. Waxaa jira baaritaano tijaabo ah in ay muujiyeen in qiimaha _Cr Re laga yaabaa xataa ka weyn.

Fikradda ah perturbation xawaare

The laminar iyo socodka dheecaan qasan, iyo sida, qiimaha muhiimka ah ee tirada Reynolds ah (Re) waxay ku xiran tahay tiro badan oo ah arrimo. From Wehliyaha cadaadiska, height of kuuskuus roughness, xoojinta qas ee socodka dibadda, heerkulka kala duwan, iwm sahlanaato, kuwaas oo arrimo wadar ahaan waxaa loo yaqaan xawaare perturbation tan iyo markii ay saamayn gaar ah oo ku saabsan heerka socodka. Haddii khalkhal this waa yar yahay, waxaa lagu gar gooyn karaan ciidamada viscous doonaya inay waafajiyaan beerta xawaare ah. Waayo, perturbations badan oo socodka noqon kartaa deganayn, iyo qas ku dhacdaa.

Marka la eego in macnaha jirka ka mid ah tirada Reynolds - saamiga ciidamada latago iyo ciidamada culus, xanaaq qulqulka daboolay by formula ah:

Re = ρuL / μ = ρu ² / (μ × (u / L )).

Sareeyaha jeer waa madaxa xawaare iyo hooseeyaha - qiimaha waa amarka of stress ka frictional, haddii L loo qaato sida dhumucda lakabka xuduud. cadaadiska Dynamic u egtahay inuu baabbi'iyo dheelitirka iyo ciidamada khilaaf this soo horjeeda. Si kastaba ha ahaatee, ma cadda sababta ciidamada tiiro (ama xawaare cadaadis) waxay keeni in isbedel keliya marka ay 1000 jeer ciidamada more viscous.

Xisaabinta iyo xaqiiqooyin

Malaha, dheeraad ah ku haboon in loo isticmaalo sida xawaaraha ah sifo Re _CR ma buuxda socodka xawaare u, iyo perturbation xawaare ah. Xaaladdan oo kale, tirada Reynolds muhiim noqon doonaa oo ku saabsan 10, i.e. marka aad iyo aad u qas cadaadis firfircoon walwalka viscous ka badan 5 jeer socodka laminar galay a socodka dareeraha qasan. Taas macnaheedu waxaa Re sida ay saynisyahano qaar ka mid ah si fiican u sharaxay by soo socda xaqiiqooyinka experimentally xaqiijiyay.

Waayo, profile a xawaare fiican u labisan on dusha a dhammaataan siman dhaqan ahaan lagu go'aamiyaa tirada Re _Cr socotaa in xad la'aan, taas oo ah, kala guurka dhab ahaan ku danbayso in qas. Halkan tirada Reynolds ah waxaa lagu go'aamiyaa baaxadda xawaare perturbation hoose qiimaha muhiimka ah, taas oo waa loo siman yahay ilaa 10.

In joogitaanka qas macmal ah, taasoo keenta Heerka sayrin dhigma heerka aasaasiga ah, socodka noqdo at aad uga hooseeya tirooyinka Reynolds qasan badan _{Cr Re,} ka qiimaha waadaxa ah ee xawaaraha goostay. Tani waxay u ogolaaneysaa isticmaalka Wehliyaha Dib _Cr = 10, halkaas oo xawaare ku caan yahay qiimaha waadaxa ah ee perturbation xawaare sababa sababaha kor ku xusan.

Stability taliskii socodka laminar ee dhuumaha

The laminar iyo socodka qasan caadi ah in dhammaan noocyada kala duwan oo cabitaanno ah iyo gaasaska xaalado kala duwan. Dabeecadda laminar of socodka waa dhif iyo waxaa lagu gartaa, tusaale ahaan, waayo, cidhiidhi bannaanka durdurrada dhulka hoostiisa. Inta badan dheeraad ah, arrintan waa walaac of saynisyahano ee macnaha guud ee codsiga wax ku ool ah gaadiidka ay biyaha dhuumaha, saliidda, gaaska iyo dareerayaasha kale.

Q xasiloonida socodka laminar waa si dhow la xiriira in ay daraasadda dhibtay mooshin socodka ugu weyn. Waxa la ogaaday in ay saameeyaan loogu yeero perturbations yar. Iyadoo ku xiran in ay koraan ama baabba'ayn muddo, socodka aasaasiga ah waxaa loo arkaa inay deggan ama deganayn.

Waayo, dheecaanka compressible oo aan compressible

Mid ka mid ah waxyaabaha saameyn ku laminar iyo socodka dheecaan qasan waa ay compressibility. Hantidaan waxaa dheecaan si gaar ah muhiim in waxbarasho ee xasiloonida ee geedi socodka non-taagan la isbeddel deg deg ah in hadda ugu muhiimsan.

Studies ayaa tilmaamaya in socodka laminar ah ee dareeraha ah incompressible in dhuumaha ee qaybta cylindrical waa adkaysi u rabshooyin axisymmetric iyo non-axisymmetric yar in waqti iyo boos.

Recently, xisaabaha lagu fuliyay on saamaynta rabshooyin on caabbi socodka axisymmetric ee qayb tubada of tube cylindrical ah meesha hadda ugu weyn ee ku xidhan tahay labada wadataa. dhidibka duwo biibiilaha waxaa loo tixgeliyaa sida dhimaya in saamayn ku profile xawaare weheliyaan gacan biibiilaha ugu weyn socodka.

gunaanad

Inkastoo qarniyo waxbarasho, ma dhihi karno in laminar oo qasan socodka si fiican loo bartay. waxbarashada tijaabooyin heerka micro, kicin arrimo cusub oo u baahan in xaq ah xisaabinta sababaysan. dabiiciga ah ee cilmi-baarista waa codsiga oo la isticmaalo: kun ee dunida ugu kiilomitir oo biyo ah, saliidda, gaaska iyo wax soo saarka. The dheer ku soo bandhigay xal farsamo ee dhimista ee qas inta lagu guda jiro gaadiidka, ayaa in ka badan wax ku ool ah in ay noqon doonto.