Here's a round-up of the day's results so far:

Round 1:

McNally/Musetti beat Osaka/Monfils 5-3 4-2

Swiatek/Rudd beat Keys/Tiafoe 4-1 4-2

Errani/Vavassori beat Rybakina/Fritz 4-2 4-2

Muchova/Rublev beat V.Williams/Opelka 4-2 5-4 (7-4)

Pegula/Draper beat Raducanu/Alcaraz 4-2 4-2

Quarter-finals:

Swiatek/Rudd beat McNally/Musetti 4-1 4-2

Errani/Vavassori beat Muchova/Rublev 4-1 5-4 (7-4)

Jack Draper speaking on court: "I've got a pretty good partner! What an experience playing out here with Jessica against Emma and Carlos. It doesn't get any better."

Jessica Pegula speaking on court: "Thanks everyone for showing up, that was such a fun atmosphere. I've played doubles a lot but not a lot recently, so that's always tricky. It was a lot of fun and Jack played great."

Draper's lightening movement at the net sets up three match points, the first of which he hits into the net, and the second Raducanu saves with an ace.

Alcaraz smashed a powerful return down the middle that Draper could only return long.

Three break points saved and Alcaraz and Raducanu are still in this!

Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows

The atmosphere fell a little flat when Raducanu and Alcaraz lost that opening set.

The DJ had to stick on the Friends theme tune to get things going again.

Then Alcaraz, ever the entertainer, took things into his own hands by bending a forehand winner around the net post.

But, despite the fun and camaraderie between Alcaraz and Raducanu, they look to be on the way out...

Draper opens the game with an ace, before Alcaraz returns into the net and Raducanu returns short.

Draper then exchanges a rally of long shots with Alcaraz before Raducanu hits the net from close range.

Great game from Draper, but Raducanu and Alcaraz are in trouble.

Alcaraz opens the game with another sweeping shot down the line which Pegula can only return long, but the Spaniard can't keep a Draper smash in bounds despite his best efforts.

The world number two then hits into the net as he stoops to meet Draper's return - Alcaraz gave the Brit too much room to work with.

Pegula's next return is long, before the American hits a powerful forehand that Raducanu defends but out of bounds.

Raducanu hits a return at the net wide and the top seeds break serve.

Alcaraz shanks a wild return into the stands, before Draper moves smartly at the net to emphatically cut out a Raducanu shot.

Raducanu then shows lightning reflexes to return a Draper smash, gives up on the point as Draper lands a drop shot, but there is Alcaraz to return along the line for the point!

It's no use though, as Draper scores from the net on the next point to equal the set.

Alcaraz and Raducanu take the first game of set two.

Alcaraz can't lift a Draper return that lands at his feet, before Pegula hits the net from deep and Draper returns Raducanu's serve too long.

Pegula does the same on the next point, but then Raducanu double faults and hits a forehand wide to take the game to deuce.

Draper does brilliantly to slide and rescue a deep shot, but Alcaraz is at the net to mop up.

While it's Alcaraz and Raducanu who appear to have better chemistry on the court, it's Draper and Pegula who impressed in that first set.

They don't know each other particularly well, but that doesn't seem to matter.

Second set starting now, Raducanu to serve.

Jack Draper serves and takes the set.

Emma Raducanu looks a little sheepish as she smashes a return straight at Pegula, who has to duck out of the way to avoid it.

Draper and Pegula recover, but the Brit spurns a first set point by hitting into the net from the baseline, before Alcaraz saves a second after a quick rally at the net.

The Spaniard then appears to take a shot off Raducanu but hits it long - that's the first set to Draper and Pegula.

Lovely stuff from Raducanu there as she meets two draper forehands at the net with perfect timing to take control of the game.

She makes it a perfect three to claim the game, with the players now having their first drinks break.

Pegula's turn to serve.

Draper goes long but then makes amends with a sharp reaction at the net. Raducanu then ever-so-slightly overhits a shot to the back of the court, before Pegula does the same with a back hand from deep.

Alcaraz commits to meet a Pegula forehand at the net but gets it all wrong and hits it into the net, before the Spaniard hit a powerful forehand out when looking for the corner. 3-1.

Emma Raducanu and Carlos Alcaraz are on the board.

A double fault from Raducanu saw her and Alcaraz fall behind, but Draper netted and then went long when returning Raducanu's serve.

The Brit's final serve was returned up in the air by Pegula, allowing Alcaraz to smash past Draper for the game.

2-0 to Draper and Pegula - Draper has had a great start to this match.

An ace from the British number one secured a 30-15 lead, before Raducanu couldn't get enough on a return.

Raducanu to serve.

Top seeds Jack Draper and Jessica Pegula break serve to take the first game.

Draper reacted quickly at the net for 0-30, before Alcaraz overhit from the base line for 0-40. Draper returned long from deep to get Alcaraz and Raducanu off the mark, but then played a superb sweeping shot over his fellow Brit to take the game.

Warm-ups done, and we're off!

Alcaraz's opening serve is returned by Draper, but Raducanu hits wide from the net. 0-15.

Jessica Pegula is the most experienced doubles player on the court in this one - will that prove the difference?

Jack Draper and Jessica Pegula win the coin toss and elect to receive first.

Carlos Alcaraz and Emma Raducanu to serve.

It sounds like Carlos Alcaraz is looking forward to playing alongside Emma Raducanu.

"I think [the concept] is good, but the scheduling is not the best to be honest," he said during a press conference on Monday.

"It's going to be new for me, I'm going to have so much fun there and playing with Emma. It's going to be tough against Draper and Pegula, but I'll try to enjoy it as much as I can.

"I'll treat it as really good and important preparation [for the Grand Slam]. I'll try to be at my best to help Emma get the win."