Serena Williams overpowered German Carina Witthoeft 6-2 6-2 to set up a third-round clash with big sister Venus at the U.S. Open on Wednesday.Williams sent down 13 aces and 30 winners to record her second consecutive straight sets victory at Flushing Meadows as the 36-year-old, who is hunting a record-equalling 24th Grand Slam title, wrapped up the win in one hour and seven minutes.”It’s always such a great crowd at night. It’s just amazing to play in front of this crowd,” she said courtside after her victory. “I was happy with a lot of things.”Next up is a 30th career meeting with Venus, who beat her younger sibling in their most recent encounter at Indian Wells earlier this year.The last time the two sisters met at a Grand Slam was in the 2017 Australian Open final, where Serena prevailed in straight sets.”It’s obviously a tough match,” Serena added.”Cheer for me…or Venus..either one will work.”@serenawilliams shares a few words about her upcoming clash against Venus…We’ll be on the edge of our seats in the meantime.https://t.co/zUjH8xQd4X pic.twitter.com/qyOVtJjrVfUS Open Tennis (@usopen) August 30, 2018″It’s so young in the tournament, but it is what it is. It’s not the end of the world. We would rather have met later. We’re both going to come out per usual and play our best in front of you guys.”Normally, I would say cheer for me. But, whoever you feeling — me or Venus will work.”advertisementSTEPHENS FIGHTS HER WAY TO ROUND What did @SloaneStephens do during the heat break today?#USOpen pic.twitter.com/h50mOYK1k3US Open Tennis (@usopen) August 30, 2018Defending U.S. Open champion Sloane Stephens overcame scorching heat, a blister and an inspired performance by qualifier Anhelina Kalinina to advance to the third round with a hard-fought 4-6 7-5 6-2 win.The third-seeded American fired an ace on match point to complete the comeback, which took 2 hours and 46 minutes on a hot and humid day on Arthur Ashe Stadium.”I wasn’t playing my best,” the 25-year-old said in an on-court interview.”It was super hot and that was no fun at all. I was sweating a lot,” she added. “But I came out in the third set bouncing around.”The 21-year-old Kalinina blitzed Stephens at the start, racing out to a 4-1 lead in their first meeting before capturing the first set to make the partisan New York crowd nervous.Stephens bounced back in the second, jumping out to a 3-0 lead before taking a medical timeout to receive treatment for a blister on the palm of her right hand.The bandage on her serving hand seemed to hamper her and Kalinina broke Stephens in the first game after the timeout and levelled the set at 5-5.But Stephens regrouped and crushed a running forehand winner to level the match and force a decider.Stephens emerged from the 10-minute heat break following the second set the fresher of the two players, committing eight unforced errors to Kalinina’s 17 as she cruised to the finish line.Next up for Stephens is hard-hitting former world number one Victoria Azarenka of Belarus, who thrashed Australian Daria Gavrilova 6-1 6-2.Despite the marathon match on Wednesday, Stephens is battle tested in New York.She won four three-setters en route to last year’s final, where she defeated fellow American Madison Keys in the straight sets to claim her first Grand Slam trophy.