Madzi, madzi ndi mpweya, ali ndi kukhuthala kosiyanasiyana. Kukhuthala kwenikweni ndi mphamvu yokangana pakati pa mamolekyu omwe amapanga madzi. Mamolekyu omwe amapanga madzi amakhuzana pamene akuyenda. Mu madzi, kukhuthala kumachitika chifukwa cha kugwirizana (kukopana pakati pa mamolekyu ofanana). Mu mpweya, kukhuthala kumachitika chifukwa cha kugundana pakati pa mamolekyu.
Madzi amadzimadzi nthawi zambiri amayenda mosavuta, mwachitsanzo madzi. Mosiyana ndi zimenezi, madzi okhuthala ndi ovuta kuyenda, mwachitsanzo mafuta ophikira, mafuta, uchi, ndi zina zotero. Mutha kutsimikizira izi pothira madzi ndi mafuta ophikira pansi potsetsereka. Madzi adzayenda mofulumira kuposa mafuta ophikira kapena mafuta. Kukhuthala kwa madzimadzi kumadaliranso kutentha. Kutentha kwa madzimadzi kukakwera, madziwo samakhala olimba kwambiri. Mwachitsanzo, mayi akamaphika nsomba kukhitchini, mafuta ophikira omwe poyamba amakhala olimba amakhala olimba kwambiri akatenthedwa. Mosiyana ndi zimenezi, kutentha kwa mpweya kukakwera, mpweyawo umakhala wolimba kwambiri.
Choyezera cha kukhuthala
Kukhuthala kwa madzimadzi kumaimiridwa ndi chizindikiro η (werengani: eta). η = kukhuthala kwa madzimadzi. Chifukwa chake mulingo wa kukhuthala kwa madzimadzi umafotokozedwa ndi kukhuthala kwa madzimadzi.
Pakati pa mbale ziwiri pali gawo lochepa la madzi. Kugwirizana ndi mphamvu yokoka pakati pa mamolekyulu amtundu womwewo, pomwe kugwirizana ndi mphamvu yokoka pakati pa mamolekyulu amitundu yosiyanasiyana. Mphamvu yokoka imagwira ntchito pakati pa mbale ndi gawo lamadzi lomwe limalumikizidwa ku mbale (mamolekyulu amadzi ndi mamolekyulu a mbale amakokana). Mphamvu yokoka imagwira ntchito pakati pa zigawo zamadzi (mamolekyulu amadzi ndi mamolekyulu a mbale amakokana).
Poyamba, mbale ndi gawo la madzi zimakhala zokhazikika (chithunzi 1). Pambuyo pake, mbale yomwe ili pamwamba imakokedwa kumanja (chithunzi 2). Mbale yomwe ili pansi simakokedwa (mbale yapansi siimakhazikika). Kukula kwa mphamvu yokoka kumasinthidwa kotero kuti mbale yomwe ili pamwamba isunthire kumanja pa liwiro lokhazikika (v ndi yokhazikika). Chifukwa pali mphamvu yomatira yomwe imagwira ntchito pakati pa m'mphepete mwa mbale ndi gawo la madzi lomwe limalumikizidwa ku mbaleyo, madzi omwe ali pansi pa mbaleyo amasunthiranso kumanja. Chifukwa pali mphamvu yogwirizana pakati pa mamolekyu amadzimadzi, madzi omwe adasunthira kumanja adakopa madzi omwe ali pansi.
Gawo lamadzimadzi lomwe lili pamwamba limakoka madzimadzi omwe ali pansi kuti asunthire kumanja, mosiyana ndi zimenezi, gawo lamadzimadzi lomwe lili pansi limasunga madzimadzi omwe ali pamwamba, kotero liwiro lamadzimadzi limasiyana. Gawo lamadzimadzi lomwe lili pamwamba limayenda pa liwiro lalikulu (v), madzimadzi omwe ali pansi amasuntha pa v yaying'ono, ndi zina zotero. Choncho v ikatsika, imakhala yaying'ono. Mwanjira ina, liwiro la gawo lamadzimadzi limasintha nthawi zonse kuchokera pamwamba kupita pansi mpaka l.
Kusintha kwa liwiro la madzi (v) logawidwa ndi mtunda womwe kusinthaku kumachitika (l) = v/l. V/l imadziwika kuti velocity gradient. Mbale yomwe ili pamwamba imatha kusuntha chifukwa cha mphamvu yokoka (F). Pa madzi enaake, kukula kwa mphamvu yokoka yomwe ikufunika kumagwirizana mwachindunji ndi dera la madzi lomwe limalumikizidwa ndi mbale (A), liwiro la madzi (v) komanso mosagwirizana ndi mtunda wa l. Mwa masamu, zitha kulembedwa motere:
Fomula ya coefficient yokhuthala
Poyamba, zidafotokozedwa kuti madzi opyapyala nthawi zambiri amayenda mosavuta, pomwe madzi okhuthala amakhala ovuta kuyenda. Kukhuthala kwa madzi kumawonetsedwa ndi kukhuthala kwake. Madzi akamakhuthala, mphamvu yokakamiza imafunikira. Pankhaniyi, mphamvu yokakamiza imafanana mwachindunji ndi kukhuthala kwa kukhuthala. Mwa masamu, izi zitha kulembedwa motere:
Zambiri:
η = kugundana kwa mphamvu
F = Mphamvu
l = Mtunda
A = Malo ozungulira
v = Liwiro
∝ = yolingana
Dongosolo Lapadziko Lonse la Ma Units (SI) la coefficient ya viscosity ndi Ns/m 2 = Pa.s (pascal second). CGS unit (centimeter gram second) ya coefficient ya viscosity ndi dyn.s/cm 2 = poise (P). Viscosity nthawi zambiri imafotokozedwa mu centipoise (cP). 1 cP = 1/100 P. Poise unit imagwiritsidwa ntchito kukumbukira wasayansi waku France, malemu Jean Louis Marie Poiseuille (wotchulidwa: pwa-zoo-yuh).
1 poise = 1 dyn . s/cm 2 = 10 -1 Ns/m 2
