Hidrológiai Közlöny 1966 (46. évfolyam)

3. szám - Bozóky-Szeszich Károly: Vízellátási csőhálózatok hidraulikai számításának néhány kérdése

Bozóky-Szeszich K.: Vízellátási csőhálózatok számítása Hidrológiai Közlöny 1966. 3. sz. 119 Bonpocbi rwflpaBJiHqecKoro pacneTa BoaonpoBOflHoií ceTH no BOflOCHaöweHHK) K. B030KU—Cecm B nepeoü rjiaBe cTaTbH cpaBHHBaioTCji oömenpHHHTbie b BeHrpHH pacMeTHbie <J)op.Myjibi Xa3ena—BuAbHMca w npHMeHjieMbie 3a nocjieaHee BpeMa (fiopMyjibi Koneöpyica—yaüma. flpii STOM (J>nrypbi 1 h 2 noi<a3biBaioT, mto no oöeHM (JiopMyjiaM nojiyMaioTCH oflHuaKOBbie noTepn Ha Tpeime, ecjiii npaBHJibHO BbiönpaeTca K03(|)<|)HuneHT peflyi<nHH a, 3aBHcamníí ot warepnajia Tpy6onpoBo«a (npH Hcn0Jib30BaHHH (JiopMyjibi Xa3eHa—BmibjíMca) n K03<})(jíHIHieHT mepOXOBaTOCTH ,,K" (npH HCn0JIb30BaHHH (|)0pMyjibi KoJieőpyKa—yaiiTa), 3aBHCjmjníí OT coctojihhíi (uiepoxoBaToCTH) TpyöonpoBOjia. BBHfly TOI O, MTO b 3arpaHime Bee Sojiee pacnpocrpaHaeToi (fwpMyjia Kojieöpyica—yaüma, T. e. Mame Bcero onpejiejiaeTCH K03(f>4>nu«eHT uiepoxoBaToeTii ,,K", b nacTOflmeií CTaTbe TaiOKé peKOMeHnyeTCH npiiMeHeHHe stoíí ({lopMyjibi. Bo emopoü rjiaBe paccMaTpiiBaeTcn BejiHMiiHa mepox0BaT0CTH no jiHTepaTypHbiM .naHHbiM. B mpembeü rjiaBe onpenejineTCsi HSMeHeHHe ko3<}>(J)nnneHTa conpoTiiBJieHHH A, (jiHrypupyiomero b <j)opMyjie KoAeOpyKa—yaüma n H3MeHeHHe yaeJibHoro conpoTiiBJieHi-ia ,,c" no (JiopMyjie (4), b 3aBHCHM0CTii ot ckopocth ABHweuHH. Ha cpueype 6. n3o6pa>KaioTCfi cooTiiomeHHíi A

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v AJIH pa3JlIIMHbIX CKOpOCTeft, TaK>Ke A Jj

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0 flJIH CKOpocTH l,ŐM/ceK. Pe3yjibTaTbi noKa3biBaioT, mto npn npene6pé>KeHHn H3MCHeHHfl A ii c no CKopocTii n npn noacTaHOBKe b (J)opMyjiy (4) BeJiHMHHbi, cooTBeTCTByroineK ckoPocth 1,0 M/cei<, noJiyMaeTCH HenpaBHjibHaa BejiHMiiHa noTepn Hanopa, ho TaKaji ouinöi<a aonyCKaeTCfl. Tanon BbiBOA no«TBep>K/iaeTCH h cpuzypoü 7. Ilpn npOeKTHpOBaHHH MO/KHO OIieHHTb TOJlbKO BCCbMa npHÖJTHHceHHO cocTOíiHHe TpySonpoBoaa, o>KHjiaeMoe Mepe3 öojieeMeHee fljiHTejibHbin nepHOfl. M3-3a 3Toro npHaeTCH cmhTaTb BeJTHMHHbl mepOXOBaTOCTH B TaÖJIHHaX CpeflHIIMH CTaTHCTHMeCKHMH BeJlHMHHaMH, OT KOTOpbIX fleHCTBHTejlbHafl mepoxoBaTOCTb TpyöonpoBOfla MoweT pa3jinMaTbC}i. MwenHo n03T0My, ecjin BejiHMHHa owHAaeMoíí mepoxoBatocth TpyőonpoBoaa npHHHMaeTCH HanpHMep K = 0,4 mm, Torsa Ha caMOM aejie OHa MonceT HMeTb n BejiHMHHbi K = 0,25, jthSo K 1,0. Ha (fiueype 7. noKa3aHbi coothouieHHH Meway A h C iuih pa3JiHMHbix uiepoxoBaTocTeíí, ,,/c" npH ckopocth 1,0 M/ceK. no (])nrype bhaho, mto npii pacMeTe ntrrepb Hanopa nojiyMaioTCH 3HaMHTejibHbie ouihökh, ecjiH mepoxoBaTocTb npHHHMaeTCH c bcjihmhhoh, pa3JinMaiOmeííCJI OT fletíCTBHTejlbHOH. 3TH OUHIŐKH 3HaMHTeJIbH0 npeBbiixjaioT oiiíhöok, nojiyMeHHbix ot npeHeöpeweHHíi H3MeHeHHeM K03({)(l)imHeHT0B K H C B 33BHCH.M0CTH OT H3MeHeHHH CKOpOCTII. ÜMeHHO n03T0.\ty ^jIH oÖJierMenHH npoeKTHpoBOMHbix paöor b CTaTbe peKOMeHflyeTCH, mto ecJiH AeiícTBHTeJibHyio BejiHMHHy mepoxoBaTocTH tomho Hejib3H onpeAejiHTb, Toraa npH Bblöope BeJTHMHHbl K03(|)(j)HHHeHT0B A H C yMHTblBajIHCb TOJlbKO AHaMeTp TpyBbI H IIiepOXOBaTOCTb ,,K", a CKopocTb He Haao yMHTbmaTb. OflHaKO yKa3biBaeTca B.viecTe c TeM Ha to, mto TaKOH cnocoő He npHroaeH HanpHMep fljiíi onpeaejieHHH skohomhmhoh pa6oTbi cymecTBywmeíi BOflonpoBOflHOH ccth. B t3khx cjiyMaax Hy>KH0 onpeaejiHTb fleiícTBnTeJibHyio mepoxoBaTocTb h cjie«yeT yMHTbiBaTb h BJiiiHHHe ckopocth (micjia PeHHOJibflca) npn onpefleJieHHH BejiMMHHbi Ah C. B maönuife VII. npHBOflHTCH BejiHMHHbi c rxh pa3jiHMHbix anaMeTpoB Tpyő h uiepoxoBaTocTeíí npH ckopocth flBH>KeHHji BOflbi v = 1,0 M/ceK. B maöAutfe IX. aakitch peKOMeHAyeMbie BejiHMHHbi mepoxoBaTocTH Ha ochoB3HHH COnOCTaBJieHHH C JlHTepaTypHbIMH flaHHbIMH. noflMepKHBaeTCH OAHaKO, MTO BejlHMHHbl mepOXOBaTOCTH ÍIJTH BeHrepcKHX yc^OBHH hywho onpeaejTHTb c noMombio H3MepeHHÍi. B nemeepmoü rjiaBe paecMaTpHBaioTCH noTepn Hanopa b TpyőonpoBoaax, b KOTOpbie nocTynaeT pacxoa BOflbi Q + Q, a BbixoflHT Q (pacxoa Q, ynoTpeGjineTcji no nyTH Ha AaHHOM yMacTKe). B BeHrpHH oöwmho npHHHMaeTCH, mto pacxofl Q, KOHneHTpnpyeTCH b kohhc yMacTKa, rfle BejiHMHHa noTepb. B CTaTbe paccMaTpHBaeTcji h Tanoíí cjiyMatt, Koraa ynoTpeöjieHHe KOHueHTpHpyeTCH b HaMaue h b KOHne yMacTKa no nojioBHHe aaHHOíí bcjikmuhh. Flpn stom noTepn Hanopa SyflyT ,,h", a fleíícTBHTejibHbie noTepH 4. Ha (})Hrype 8 noKa3aHbi cooTHomeHHH h'/h w h"/h h aejiaeTca BbiBOfl, mto pa3aejieHHe noTpeöjieHiiji Q, Ha aBe paBHbie MacTH Booöme pa3peaaeTCH. TaKOH cnocoő hbjijieTCH BbirOflHbIM TJiaBHblM 0Öpa30M npH KOJlbUeBOÍÍ ceTi-r, Kor^a pacMeTbi BbinojiHflK)TC5i no MeTOfly Kpocca. Prohlems arising in (he hydraulic design of water supply nelworks By K. Bozóky-Szeszich Hazen—Williams' commonly used formula and the Colebrook—White formula whose application ís beginning to spread in Hungary are compared in the first part of the present paprr. As illustrated in this eonnection by Figs. 1 and 2, friction losses obtained by using either of the two formuláé are of the same order of magnitude, provided that — when using the Hazen— Williams formula — the reduction coeffieient a, which depends on the material and eondition (roughness) of tho pipe. respectively — when using Colebrook—White's formula — the roughness k are correctly adopted. In view of the faet that the Colebrook—White formula is gaining in popularity abroad and data on the roughness k found in increasing numbers, the use of this formula is recommended in this paper. The seeond part contains oonsiderations about the order of magnitude of roughness, based on data found in the literature. In part three c.hanges with veloeity of the resistance coeffieient A in Colebrook—White's formula, respectively, that of the spécific resistance c obtainable from Eq. (4), are investigated. Values and c

v pertaining to different velocities ai'e shown in relation to values respectively c,.

0 pertaining to the veloeity 1.0/sec. llesults revealed that by neglecting changes of the coefficients A and c with veloeity and by using their values pertaining to veloeity 1.0 m/sec in Eq. (4), an incorreet value is obtained for head loss, but the error remains within acceptable limits. This conclusion is cori'oborated by Fig. 7. In the design period the eondition of the pipe after a certain length of time cannot be estimated accurately. Consequently, íoughness values found in different tables must be regarded as statistical averages only, from which actual roughnesses may differ appreciably. Thus for instance if the anticipated roughness of a pipe is estimated at k — 0.4 mm, the actual value may rangé from k = 0.25 to k = 1.0 mm. Ratios of A and c values pertaining to veloeity 1.0 m/sec but to different roughnesses k are demonstrated in Fig. 7. It will be perceived from the figure that the error in head loss computation, resulting from the assumption of a roughness different from the actual one, may be appreciably higher than that due to any neglect of changes of A and c with veloeity. In order to facilitate design work it is ,therefore recommended in the paper to adopt the following procedure : in cases where actual roughness cannot be determined accurately, values for the coefficients A and c should be assumed on the basis of the pipe diameter and the estimated k value only, but dependence on veloeity should be neglected. It is concluded, however, at the same time that this proeedure is unsuited to problems such as the determination of economic operation for an existing major water works. In such cases actual roughnesses must be established and in determining A and c the influence of veloeity (Reynolds number) must alsó be taken into consideration. ' c values pertaining to different pipe diameters and roughness values have been compiled in Table 7. for a veloeity of v — 1.0 m/sec, while in Table 9. data from various literary sources are compared and roughness values are recommended for practical use. It is cautioned, however, that roughnesses corresponding to conditions in Hungary must be determined by measurements. Part four is concerned with head losses occurring in pipelines with an inflow Q Q

1 and an outflow Q (Q, is the discharge consumed along the pipeline section). In Hungárián practice the consumption Q

1 is concentrated at the end of the section in which case